Downing Street has accused Brexit opponents of trying to tie negotiators' hands in the upcoming discussions with the European Union.
The accusation comes at the start of the Government's appeal against a High Court ruling that Theresa May must consult MPs before triggering Article 50.
Both Labour and the Liberal Democrats have signaled they would amend a motion coming before Parliament, with Jeremy Corbyn saying he would try to ensure issues of market access were key to the negotiations.
The Prime Minister's official spokeswoman said the Government wanted "everyone to be coming together" to focus on getting the best results for Britain from the process.
She said: "While others are seeming to make clear that they want to frustrate the will of the British people by slowing down the process of leaving and trying to tie the Government's hands in negotiation, the Government is getting on with respecting what the British people decided and making a success of Brexit.
"We are seeking to provide certainty where we can by saying we will trigger Article 50 by the end of March and that we are very clear there will be no going back.
"If you are backing the UK team, you want them to be able to go into the negotiation and get the best deal possible.
"It's very important that we are able to get the best deal possible, and that means not having our hands tied in negotiation.
"That's why now we want everyone to be coming together to focus on how we get the best deal, supporting the approach the UK will take in what will be a difficult negotiation where there will be us and 27 others.
"This will enable the Government to have the strongest position going into that negotiation, so we can get the right deal."