Peers will today begin five days of scrutiny of the government's Brexit bill, with Labour tabling a series of amendments.
This afternoon will see the start of two days debate on the bill's second reading in the upper house, with 190 peers down to speak.
The committee stage, when there could be votes on some of the amendments, will take place next week.
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The government, which does not have a majority in the Lords, may well face defeat on some of the amendments, which cover issues such as EU citizens' rights and whether Parliament will get a "meaningful vote" on a draft Brexit deal.
If amendments are passed in the Lords they will have to go back to the House of Commons, but it looks highly unlikely MPs would accept any changes to the bill, which passed its Commons stages unamended earlier this month.