BORIS Johnson’s former ethics adviser has said he quit because he “could not be a party to advising on any potential law-breaking”.

Lord Geidt resigned on Wednesday saying he had been forced into an “impossible and odious” position after being asked to advise on a trade issue.

It was portrayed by Downing Street as an unexpected falling out over steel tariffs, rather than the partygate scandal, which had pushed Lord Geidt to the brink of leaving his post.

However Lord Geidt has now clarified his position to make it clear that his decision was not “limited to some narrow and technical consideration of steel tariffs”.

Trying to end “confusion” caused by his “cautious language”, he said his problem was being asked to give advanced cover to the Prime Minister potentially breaching international law.

In a letter to MPs, he said: “Emphasis on the steel tariffs is a distraction. 

“It was simply one example of what might yet constitute deliberate breaches by the United Kingdom of its obligations under international law, given the Government’s widely publicised openness to this.

“Although explicit reference to international law was removed from the Ministerial Code in 2015, it is widely still held that a breach of international law would, in turn, represent a prima facie breach of the Ministerial Code. 

“Moreover, there is no explicit derogation, no lef-off written into the Code to absolve individual Ministers of their own obligations under the Code in such circumstances.

“Accordingly, and conscious of my open obligations under the Seven Principles of Public Life (Including integrity), I could not be a party to advising on any potential law-breaking.”

The update will fuel suspicions that Lord Geidt, who advised the PM on the Ministerial Code, was asked for the first time to give a view on a trade issue to compel him to resign.

In Wednesday’s resignation letter, Lord Geidt wrote: “I was tasked to offer a view about the Government's intention to consider measures which risk a deliberate and purposeful breach of the Ministerial Code. 

“This request has placed me in an impossible and odious position. 

“The idea that a Prime Minister might to any degree be in the business of deliberately breaching his own Code is an affront.

“A deliberate breach, or even an intention to do so, would be to suspend the provisions of the Code to suit a political end. 

“This would make a mockery not only of respect for the Code but licence the suspension of its provisions in governing the conduct of Her Majesty's Ministers. I can have no part in this.”