The more I see of Andy Burnham, the more certain I am that Donald Trump was right to dismiss him as the 'mayor of a town'.

Nothing wrong with being a mayor of a town, of course, but the job doesn't usually prepare you for making big decisions, especially on the international stage.

Our unelected Prime Minister's most recent blunder about being 'open' to apologising for Britain's role in the slave trade could cost us billions of pounds. It is the latest example of his infuriating – and dangerous – tendency to think aloud.

He did it over Scotland last month when suggesting that another Scottish referendum could be held if public opinion showed a demand for one. Arguably it already does. What Burnham said off the top of his head contradicts the policy of successive governments. He was forced to backtrack.

Andy again shot from the hip when he stated he wanted 'an honest discussion' about free movement, membership of the single market and rejoining the EU. He casually drops these bombshells without considering the damaging political fallout.

His comments about apologising for slavery are the most destructive so far because they come before heads of Commonwealth nations meet in the West Indies. Many Caribbean leaders are clamouring for vast reparations for slavery, which one imaginative UN judge has put at £18trillion.

That is six times our stratospheric national debt, and also roughly six times as much as the value of all the goods and services produced by this country in a year.

Until last Thursday, the British Government's official position was that it was desperately sorry the slave trade happened. And rightly so. Slavery was an abomination.

King Charles has repeatedly said as much over the past week during his tour of the Caribbean, and it's what he'll say again tomorrow at a gathering of Commonwealth leaders in Antigua. He will speak about the slave trade with 'unflinching honesty' and 'sincere sorrow'.

But what he won't do is to offer an apology, which is not yet the official position of the British Government despite the loose mouth of our chumpish Prime Minister.

An apology – as opposed to an expression of sorrow – carries an admission of fault, and therefore of potential liability. Although Burnham has rejected the idea of compensation, he has taken us a step closer to that outcome by advertising his openness to an apology.

No wonder his words were warmly greeted in the Caribbean. Dorbrene O'Marde, chair of the Antigua and Barbuda reparations support commission, said his organisation welcomed the statement as 'a movement in the correct direction in the interest of reparatory justice and humanity generally'.

Predictably the body rejected 'the decision that financial reparations will not be on the table'. Yet, whether the Prime Minister likes it or not, he has virtually put them there.

The truth is that the notion of an apology in this context is intellectually fatuous. We can feel regret for what our forefathers did, whether in relation to slavery or other abuses, but we can't apologise on behalf of long dead people for making decisions over which we had no control.

This distinction between regret and sorrow on the one hand, and apology on the other, is crucial. We can feel sorry about the evils of the past but we cannot be sorry for them because we played no part in perpetrating them. In short, we were not, and are not, responsible.

It's understandable that some people feel so sad about what was done to victims of the slave trade that they wish to compensate their descendants, although there isn't much logic in this position, since the descendants of a system that ended nearly 200 years ago in the British Empire are not themselves victims.

What cannot be accepted is that the British Government has a moral or legal obligation to make financial reparations. Yet I fear it won't be long before Andy Burnham agrees that we do. He'll probably say he wants to have another 'honest discussion' about it.

Why Britain? That is my question. Why are Caribbean leaders demanding huge amounts of our money? It must partly be because we are a relatively rich country while theirs are mostly poor. I believe they also see weakness and intellectual confusion in our leaders.

The Ottoman Empire practised slavery on a vast scale over hundreds of years yet, so far as I am aware, no one is asking modern-day Turkey to pay reparations to countries in Europe and the Middle East, from where millions of inhabitants were captured and enslaved by the Ottomans.

From the 7th until the middle of the 20th century, Arab slave traders enslaved millions of Africans. Does anyone stand up in the United Nations and demand compensation from oil-rich Arab states?

African leaders were also involved in the slave trade on a considerable scale. For example, the Ashanti in modern-day Ghana traded slaves after the British Empire made it illegal to do so in 1807. Slavery itself was outlawed by Britain in 1833.

Indeed, British wars against the Ashanti in the 19th century were partly motivated by a desire to stamp out the slave trade and domestic slavery. Yet, wonder of wonders, Ghana is today leading a campaign for reparations and apologies from which the Ashanti are exempted.

Between 1808 and 1860, the Royal Navy freed tens of thousands of slaves being shipped across the Atlantic, with many British soldiers and sailors dying in the endeavour.

I don't want to sound paranoid but the sins of our forefathers are better remembered than those of other nations, and the efforts of the British to extirpate slavery while others were still practising it are generally forgotten.

Yet it is Britain that finds itself repeatedly in the dock – as it will be again this week when the King is required to abase himself in front of Caribbean leaders. Isn't it time other countries also expressed regret?

Moreover, there have been many outrages committed by other nations that have nothing to do with slavery. Are we to seek reparations from Germany for its militarism? Or from France because Napoleon rampaged across Europe?

Of course not. The perpetrators are dead, the victims are dead. The sins are not forgotten, but they can't be blamed on present generations, and present generations can't be expected to pay us compensation.

I repeat my question. Why is Britain targeted more than any other country, and why do we, almost uniquely, wallow in guilt and self-loathing? It should not be so.

In an article in yesterday's Observer newspaper, Andy Burnham portrayed himself as an apostle of hope. 'I will keep talking about hope,' he wrote, 'and won't stop until people can feel it.'

I don't know why he thinks that potentially involving us in billions of pounds of reparations will make us feel hopeful. Nor is a politician whose overriding objective is to fill us with hope the person we need in this perilous hour.

Our garrulous Prime Minister was surely intended by God to be a city mayor. He mounted a coup, seized power – and now this ill‑suited leader is trying to run the country.