Brexit Secretary David Davis is facing questions in Parliament ahead of the Government formally giving the EU its notice to quit the bloc next week.
Mr Davis is appearing before the Lords EU Committee on Wednesday in the wake of failed attempts by peers to try to amend the legislation which gave the Prime Minister the power to trigger Brexit.
The Commons rejected bids by the Lords to secure the rights of EU migrants and ensure Parliament had a "meaningful" vote on the final outcome of talks, but both issues remain of considerable concern in the upper house.
The scrutiny comes as Theresa May faces her first Prime Minister's Question Time since announcing she would trigger Article 50 of Lisbon Treaty and set in train two years of withdrawal negotiations on March 29.
Despite ministers warning that no deal is better than a bad deal, the Lords EU Internal Market Committee has warned of the risk of "serious harm" to Britain's non-financial service sector if the UK fails to hammer out a trade agreement with Brussels.
Peers expressed concern that without appropriate deals, British broadcasters could lose the right to sell programmes to European markets, UK airlines may have to relocate to the continent and the viability of events like London Fashion Week could be brought into question.
EU leaders will wait a full month after the formal notification of withdrawal before they gather on April 29 to discuss their stance.
European Council president Donald Tusk said the 27 non-UK leaders would meet then to set-out guidelines for what are expected to be gruelling negotiations ahead which must be completed by the end of March 2019.
Mrs May told the Cabinet that invoking Article 50 would be a "historic event" which would provoke "a shift in our role in the world".
One remaining cause of major tension ahead of the start of Brexit talks is calls for the UK to settle a "divorce deal" bill of up to £50 billion as part of withdrawal.