Asked if the Government had drafted a clause for the Withdrawal Agreement which would have allowed the United Kingdom to opt out of the backstop unilaterally, Mr Robbins said: "Ministers asked us to look at a whole range of options for how to bring the backstop to an end, and so we did".
Although the contempt offence is hundreds of years old, only a handful of MPs have been suspended and no Cabinet minister has ever faced the charge.
"That's why we had a debate in parliament, to say: is this the sort of case where it's so exceptional that it should be disclosed?"
"Thus, the choir screaming about deficiencies in the Prime Minister's Brexit plan has become very vocal, with several MPs in turn pointing out that the deal is far from gaining a majority".
Now, however, it says only that Cox will make a statement to Parliament.
"This is, after all, not a general election and the Government or the opposition can not be allowed to play fast and loose with representative democracy", they said.
Jacob Rees-Mogg accused Cox of not explaining why ministers were refusing to comply with the Commons motion. "It is no longer a matter for the Government to judge, it has been decided by this House, which is a higher authority".
May's government is also facing a battle in Parliament over confidential advice from the country's top law officer about the Brexit deal.
The 43-page Legal Position On The Withdrawal Agreement was published after the Government lost a parliamentary vote calling for the full legal advice to be released.
"I think that's important for us as politicians to remember that".
But he was also there not just to defend the prime minister, but to try and sell her deal to recalcitrant Conservative MPs by attempting to reassure them that her Brexit compromise - despite having "unattractive, unsatisfying elements" - was not going to trap the United Kingdom into a customs union with the EU forevermore.
At a rowdy session of parliament, Attorney General Geoffrey Cox outlined the legal advice he had given to the government, including over a "backstop" arrangement to prevent the return of a hard border between Northern Ireland and EU member state Ireland if a future UK-EU trading deal is not reached in time. May spoke with small groups of backbench MPs in her Commons office throughout the day.
Mrs May will also address the Commons as she tries to persuade MPs to support her Brexit deal in that vote on 11 December. Both Conservative and Labour manifestos at the last election said they respected the leave vote in the 2016 referendum.
Earlier, Japanese Prime Minister Shinzo Abe urged May to ensure stability as Britain leaves the European Union and asked her to do what she could to avoid a "no deal" Brexit.
Over 100 Tory MPs are reportedly likely vote against the withdrawal agreement next week, according to lists compiled by Buzzfeed News and the Guardian.