Boris Johnson has rounded on Keir Starmer over his 'pathetic and tragic' decision to water down sanctions on Russian oil.

The former prime minister led a chorus of disapproval over Labour's decision to shelve plans to close a loophole in global trade rules that allows diesel and jet fuel produced from Russian oil to be imported.

The decision also triggered a backlash in Ukraine. On Wednesday there were warnings it could derail a planned meeting between Sir Keir and Ukrainian President Volodymyr Zelensky.

Anger over the decision was compounded after it emerged it was slipped out on Wednesday night as Labour MPs were voting through a ban on new oil and gas licences in the North Sea to meet Ed Miliband's Net Zero goals.

Mr Johnson told the Mail that Sir Keir should 'sack Ed Miliband and back Ukraine'.

He added: 'Britain has been one of Ukraine's best and most reliable allies for four years. We are now betraying the Ukrainians in the most pathetic and tragic way.

'You can't go soft on Putin. I do not believe this decision will make a jot of difference to consumers in the UK. But if you are worried about a shortage of UK hydrocarbons, then sack Ed Miliband.'

During angry clashes in the Commons, Sir Keir insisted he was not lifting sanctions 'in any way whatsoever'.

But officials later confirmed that a planned crackdown on imports of Russian oil refined in third countries like Turkey has been postponed. Embarrassingly for the government, the crackdown, which was first announced in October last year, is expected to go ahead in the EU while it remains on hold in this country.

The move comes amid mounting government concern about the impact of the Iran war on critical supplies like jet fuel and diesel.

Kemi Badenoch accused the PM of 'choosing to buy dirty Russian oil'. She added: 'That money will be used to fund the killing of Ukrainian soldiers. Isn't he ashamed?'

Rounding on the PM, the Tory leader said: 'He is importing sanctioned Russian oil, nationalising steel and imposing price controls in the supermarket—it is like the Soviets won.'

Sir Keir accused Mrs Badenoch of 'misrepresenting' the facts. He claimed it was 'standard practice' to phase in new sanctions over time. And he insisted that other parts of the package meant the pressure on Moscow would ramp up.

However, the move caused alarm across the political spectrum.

Emily Thornberry, chair of the Commons foreign affairs committee, also criticised the move.

She told the BBC: 'We are talking about our allies in Ukraine who have been fighting a war bravely against Russia for years and years with our support.

'They have looked to Britain as one of their most important allies, and they don't understand, given that we promised that we would stop this loophole in October, and we still haven't done it. In fact, it seems to have got worse. People feel very let down.'

Ukrainian sources claimed the decision could wreck plans for a meeting between the PM and President Zelensky in the coming days. Downing Street declined to comment, but a Whitehall source described the claim as 'mischief making'.

Ukrainian MP Oleksiy Goncharenko told the Mail the decision would 'encourage the aggressor'.

He added: 'This is a big mistake by Keir Starmer, both morally and strategically. I hope that he will change his mind and change his decision.'

Ukrainian soldier Oleksandr Monchak told the Mail: 'I would ask Mr Starmer to come here and see with his own eyes what it is like to live through war.

'Then perhaps he would better understand what life and freedom cost us, and perhaps he would stop bargaining over us behind our backs, over gas and oil deals.

'The war criminal Putin and his entourage are encouraged by you. They are not stopping precisely because of policies like this.'

Peter Dickinson, editor of Ukraine Alert in Kyiv, said: 'Anyone who understands the mentality of the Putin regime will tell you that the UK's decision sends a disastrous message to Moscow.

'Loosening sanctions on Russian oil relaxes the pressure on Putin and confirms his long-held belief that despite the tough talk of many Western leaders, they are all ultimately driven by money and can always be bought off.

'Putin remains confident that he can outlast the West in Ukraine. This move by the Starmer government will make him more determined than ever to ride out his current difficulties and continue the war.'

Shadow energy secretary Claire Coutinho said it was a 'moral disgrace' for Labour to block new production in the North Sea while importing Russian oil products.

'Labour are funding Putin's war machine by lifting sanctions on Russian oil, whilst they block Britain from drilling in the North Sea,' she said.

'It is a moral disgrace but the logical consequence of Ed Miliband's policies who wants to lecture us about climate leadership whilst replacing British production with high emission imports. Putin must be laughing at his naivety.'

British volunteer Ethan Harcourt told the Mail from the front line: 'From the Ukrainian perspective, I thoroughly understand their anger at the moment.

'This is yet another letdown.'

Russian opposition politician Ilya Ponomarev, who fled Moscow for Kyiv, said: 'Ukrainians feel betrayed.

'After so many bold statements about 100 years of friendship and standing together, this is a gesture that leaves a sour taste.'