Theresa May has cast doubt on Britain's relationship with the European single market during any post-Brexit transitional period.
The Prime Minister was challenged by Labour former minister Pat McFadden to say if her "red line" on leaving the single market applied to any transition period after March 2019.
Mrs May replied: "We said we would no longer be members of the single market because we will no longer be members of the European Union and there are the four pillars, as the European Union consistently says.
"The four pillars are indivisible, and therefore the other issues that we wish also not to be subject to like the European Court of Justice and free movement requirements mean that we will no longer be members of the single market.
"At the end point, when we have at the end of the two years negotiated the end state deal, there will then be an implementation period for that deal.
"But we're very clear that at the point at which we reach the end of those negotiations we will be out of the European Union."
Downing Street aides later declined to discuss the details of Britain's transitional deal, which they said would form part of Brexit negotiations.
Speaking at Prime Minister's Questions, Mr McFadden had said: "In her Lancaster House speech the Prime Minister said that the UK would be leaving the single market.
"Can she tell the House whether that red line on the single market also applies to any transition agreement or implementation period that might be agreed for the period after March 2019?"
Later, Brexit Minister Robin Walker said the UK must retain the ability to impose sanctions on other nations after leaving the EU, as MPs debated the future of such penalties after Brexit.
Mr Walker said the UK needed "as many tools as are available" to counter threats from abroad, although he insisted Britain would still work with allies within the EU.
He said: "This is more about powers than it is about policy and the UK wants to pursue a consistent policy as we go forward, but we'll need powers as we are exiting the European Union in order to do so.
"The UK's implementation of both UN sanctions and European Union multilateral sanctions currently relies on the European Communities Act of 1972 and the UK has some limited domestic powers to impose sanctions, notably in domestic counter-terrorism, but these aren't sufficient to replicate the range of sanctions currently in force through the European Union."
New legislation will be introduced during this parliamentary session to allow the UK to make decisions on implementing non-UN sanctions, he said.
Labour's Helen Goodman (Bishop Auckland) said it was "vital" for the UK to be able to make decisions on sanctions and pressed the Government on when its plans would be published.
She said the lack of detail revealed the "chaos and confusion" going on behind the scenes of the Brexit process.
SNP shadow trade and investment spokeswoman Hannah Bardell warned against the UK relaxing sanctions in favour of trade with allies.
She said: "There must not be any serious divergence from EU partners in sanctions.
"The UK must not relax any sanctions that are materially more restrictive than existing or new EU sanctions, especially where the UK has significant trade with a particular country.
"Many have raised concerns that the UK may be dragged onto the new US President's rather unpredictable turf.
"For example, as president elect he severely criticised the joint comprehensive plan of action with Iran.
"If he were to oppose new sanctions on Iran, there might be pressure on the UK and our special relationship to follow suit."