Kemi Badenoch last night launched a fierce Brexit broadside at her current Cabinet colleague Lord Cameron, appearing to accuse him of a 'dereliction of duty' over the 2016 vote.

The Business Secretary criticised the Foreign Secretary for not planning for a Leave win because he was leading the Remain campaign before the seismic plebiscite. 

In a speech to the CBI last night Ms Badenoch, seen as a leading contender from the Tory Right to become the next party leader, lashed out at her colleague over events that happened before she was even an MP. 

Mr Cameron, along with Jeremy Corbyn, led the Remain campaign which lost 52 per cent to 48 per cent in June 2016. He resigned as prime minister and left Parliament altogether later that year. But he was brought back as Foreign Secretary by Rishi Sunak in a shock move in November.

According to Politico Ms Badenoch, who became MP for Saffron Walden in Essex in 2017, told the lobbying group: 'One of the most disappointing things was becoming an MP a year later and finding out there had been no plans made about how this was going to happen. I think that was the real dereliction of duty.

'If you're offering people Leave vs Remain you need to do your work, not just do the work for the option you want to win.' 

The Business Secretary criticised the Foreign Secretary for not planning for a Leave win because he was leading the Remain campaign before the seismic plebiscite.

In a speech to the CBI last night Ms Badenoch, seen as a leading contender from the Tory Right to become the next party leader, lashed out at her colleague (pictured on a diplomatic visit to Mongolia today) over events that happened before she was even an MP.

Before the vote the then PM came under fire from his own Tory MPs over a letter sent out by Britain's top mandarin telling civil servants they were banned from giving any help to Eurosceptic ministers, who will not even be allowed to see papers relating to the work of their own department. 

The letter, sent by the late Cabinet Secretary Jeremy Heywood to all civil servants, sets out strict rules on their behaviour in the run up to the EU referendum.

It stated that government resources, from briefing notes, speech preparation and research, must only be used in the referendum campaign if it supports the Government's official stance in support of Britain's membership of the EU.

But at the same time ministers and advisers who back Britain staying in the EU were free to use government papers and other resources to support their case. 

Challenged at the time in the Commons, Mr Cameron said: 'The Government's position is that we will be better off in a reformed European Union.

'Ministers are free to part from that position and campaign in a personal capacity, that is, I think, a very important statement, it's right in terms of how we go about it, but it does not mean the Government is neutral, it doesn't mean the civil service is neutral, the Government has a policy from which people can depart.'