David Davis’s department said last year that it was preparing “an assessment of the impact of exit on over fifty sectors of the economy”, undermining his recent claim that the Brexit impact studies do not exist.

The comment was made in a Freedom of Information response from November 2016, suggesting that work was underway on the documents more than a year before the government backtracked on acknowledging their existence.

In addition, the Guardian has found at least 12 references in Hansard, the official record of parliament, to ministers talking about the work to “assess the impact” or “assess the economic impact” of Brexit over the last year.

The findings are likely to fuel suspicions that the Department for Exiting the European Union does have documentary evidence of the impact of Brexit on the economy.

Parliament asked for 58 impact assessments to be handed over to the select committee on exiting the EU last month, so they could examine how Brexit would affect different sectors.

But MPs who were allowed to view the 800-pages of documents ridiculed the analyses for simply setting out the current situation for businesses, explaining how the EU operates and then providing a section on what stakeholders think.

Davis and other ministers claimed they had never said any “impact assessments” existed, and the committee, which is dominated by Conservatives, ruled that he was not in contempt of parliament for failing to release such documents.

However, campaigners believe the government does still hold relevant information setting out the official view of how Brexit could affect the economy and businesses.

A judicial review has been launched by Green MEP Molly Scott Cato, and the Good Law Project, led by Jolyon Maugham, to try to force the government to reveal any analysis of the impact of Brexit but it is not certain this can be completed in time.

Launching the review, Scott Cato said: “There are two possibilities. Either the studies do exist, and Davis has lied to the House and must resign. Or the studies do not exist, in which case Davis is guilty of dereliction of duty and must resign. Either way, he cannot maintain the confidence of the House as our Brexit negotiator.”

Asked about the repeated use of the words “impact” and “assess” to describe the documents, the government has changed tack to claim that the documents released to the House of Commons do in fact analyse the impact of leaving the EU.

A spokesman for the Department for Exiting the European Union pointed to recent comments in the House of Commons by Robin Walker, who denies the existence of impact assessments, but said: “The information that has been shared with the select committee and is available to all members of this House in the reading room includes assessments of the impact on the regulatory matters and of the importance of EU trade to different sectors.”