LONDON: Britain's upper house of parliament has been given "a pretty powerful message" to pass legislation to start Brexit talks and not delay British Prime Minister Theresa May's timetable for leaving the European Union, a government minister said on Sunday.

In interviews with local media, David Lidington, the leader of the lower house of parliament, said the unelected upper chamber should respect the vote to leave the EU at last year's referendum and the support given by the House of Commons.

Members of the Lords from the opposition Liberal Democrats say they will try to attach conditions to a bill giving May the right to trigger Article 50 of the EU's Lisbon Treaty, which may derail a pledge to launch divorce talks by the end of March.

"The fact that the exit bill, the Article 50 bill, has gone to the House of Lords with a majority of more than 300 from the House of Commons and unamended ... is a pretty powerful message to the lords," he told the BBC's Andrew Marr Show.

"Of course they are free to propose and debate amendments, I hope they will also take full account of the strength of opinion from the elected house."

May won approval from the lower house earlier this month and the House of Lords, where her ruling Conservative Party does not have a majority, is due to start debating the bill on Feb. 20.

Dick Newby, Liberal Democrat leader in the Lords, told Sky News that his hope to attach amendments -- including one calling for a second referendum on a final Brexit deal -- to the bill was not an attempt to "block" legislation or to slow it down.

The Liberal Democrats have also put forward a second amendment which would require the government to guarantee the rights of EU citizens resident in Britain and British citizens living elsewhere in the EU.

If the amendments are carried, the modified bill will return to the lower house for approval. The bill can be passed back and forth until they agree.

EU officials are keen to know when May will trigger Article 50, but Lidington said only that the prime minister was still "on course" to deliver on her pledge to launch talks before the end of March.

Asked on ITV's Peston on Sunday show whether May could bring the Article 50 letter to an EU summit on March 9-10, Lidington said he could not discuss firm dates as the timing depended on how long the Lords take to debate the bill.

"If all goes to plan then the bill will get 'Royal Assent' (to become law officially) at some time in middle March," he said.

"What the PM has always said is that she would trigger Article 50 before the end of March, 2017 ... so I think we are on course to deliver on that."