Ministers were today warned they could be held in 'contempt of Parliament' after refusing to publish the full legal advice on Theresa May's Brexit deal.

The views of Attorney General Geoffrey Cox on whether the UK will be locked into the so-called Irish border 'backstop' are thought to have been crucial in the package being passed by Cabinet.

Earlier this month the Commons endorsed a 'Humble Address' tabled by Labour demanding the opinion be released.

But Chancellor Philip Hammond insisted today that only a summary of the advice will be released, warning it would be 'impossible for the Government to function' if such confidential material was made public in full.

Labour has appealed for Speaker John Bercow to intervene - and he said this afternoon that he will consider whether Parliamentary rules have been broken.

The views of Attorney General Geoffrey Cox (pictured right) on whether the UK will be locked into the so-called Irish border 'backstop' are thought to have been crucial in the package being passed by Cabinet. Philip Hammond (left) said the full advice would not be released

Both Labour and Tory Brexiteers have been urging the release of the advice in full as they try to sink the package thrashed out by Mrs May with Brussels.

Shadow Brexit secretary Sir Keir Starmer today asked the Speaker what he could do to force the Government to play ball - and said he was 'deeply concerned' at the refusal to comply.

Mr Bercow said Labour should write to him 'to suggest the House has been or is about to be subject to a contempt'.

He added: 'I will decide - and I will not linger - whether there is an arguable case that a contempt has been committed and therefore whether an appropriate motion should be put urgently to the House.'

Earlier, Sir Keir said the summary would not be 'good enough'.

'Parliament won the right to see the full legal advice and that is precisely what we expect to see. Labour will not let ministers off the hook,' he said.

He has written to ministers demanding the information is published soon.

Veteran Tory Eurosceptic Sir Bill Cash said a 'reasoned political statement' would not be enough.

'The position, in a nutshell, is going to be about the question of whether or not the EU has a veto over our leaving the backstop in Northern Ireland.

'This is absolutely crucial because if that were to be the case and the EU does have a veto, then we'll never be able to leave the EU or strike trade deals.

'So, it's that important.'

Sir Bill rejected the idea that publishing the full legal advice on the Brexit deal could have a 'chilling effect' on future advice given by the Attorney General.

The Tory MP said there were lots of precedents where the full reports were published, such as in the run-up to the Iraq War.

However, asked on BBC Radio 4's Today programme if it was right to release the full comments, rather than a shortened summary, Mr Hammond said: 'No, there's a very important principle here, that the Government must be able to commission impartial legal advice which absolutely tells it like it is to enable it to shape its decisions, while always complying with its legal obligation in the negotiations.

Shadow Brexit secretary Sir Keir Starmer said the summary would not be 'good enough'

'It would be impossible for Government to function if we create a precedent that the legal advice that the Government receives has to be made public.

'We must have, as every other citizen has, the right to take privileged legal advice which remains private between the lawyer and the client.

'So the client has the ability to ask the difficult questions, to receive full and frank legal advice, and then to make a decision based on that full and frank advice.'

The Prime Minister's official spokesman said yesterday that the Government's position had not changed.

'This is for a full reasoned position statement laying out the government's political and also legal position on the proposed Withdrawal Agreement and attached protocols,' the spokesman said.

'The commitment remains as set out a couple of weeks ago.'