LONDON (Reuters) - Britain’s unelected House of Lords flirted on Monday with changing the conditions under which the country will announce its departure from the European Union, threatening to attach amendments to Prime Minister Theresa May’s legislation.

A detail is seen from a copy of the Brexit Article 50 bill, introduced by the government to seek parliamentary approval to start the process of leaving the European Union, in front of the Houses of Parliament in London, Britain, January 26, 2017. REUTERS/Toby Melville

The Lords, the upper chamber of parliament comprising mainly veteran politicians and business leaders, began detailed debate on approving the triggering of Article 50, the formal divorce notice May plans to lodge with the EU in March.

Earlier this month the powerful House of Commons passed the enabling legislation without amending it. Any changes made in the Lords would need approval by the lower house.

The legislation is not expected to be blocked by the Lords, but the government could be pressed into changing its plans as it does not have a majority in the upper house -- something it has so far been reluctant to do.

Among the amendments due to be considered during two days of debate are those on the rights of EU nationals in Britain; on Northern Ireland, which will share a land border with the post-Brexit EU; on a parliamentary vote on the final Brexit deal; on a second referendum on the deal; and on seeking to remain in the EU’s single market.

Votes on the key issues are not expected until Wednesday and then again next week.

Some members of the Lords hope they can force the government to give concessions, but interior minister Amber Rudd said on Sunday that she did not think there was any possibility the government would agree to any amendments.

“This is a process bill. It’s just about beginning the process for the two years that we’re going to need the time in order to prepare for leaving. Then within that there’ll be the opportunities to debate and discuss,” she told ITV.

“The elected house voted it straight through. We want the House of Lords to do the same.”

Lords are expected to press the government to write into the bill a promise it made verbally in the House of Commons: that it would give lawmakers a vote on Britain’s final Brexit deal before it was discussed by the European Parliament.

They also want the power to send May back to the negotiating table if parliament rejects the Brexit deal and for the government to guarantee the rights of EU citizens currently living in Britain.