Lord Lisvane suggested the Lords could force Mps to 'think again' on Theresa May's Brexit bill
Lord Lisvane, who served as clerk to the House of Commons as Sir Robert Rodgers for three years until 2014, said peers "could not, would not and should not" seek to halt or alter the triggering of Article 50.
The Bill will come before the Lords tomorrow, having been voted through by MPs by 494 to 122 earlier this month.
"I don't think that there's any chance that the Lords will delay the Bill," Lord Lisvane told BBC Wales Sunday Supplement programme.
"If the elected house has decided not to do so, then the unelected house could not, would not and should not do so."
The crossbencher, who had supported the call for Article 50 to go before Parliament, said he felt the process had been worthwhile.
"It's made ministers defend their position, which is an important part of the Parliamentary process," he said.
But asked if the Lords would try to amend the bill, Lord Lisvane said it was possible the house might ask the Commons to "think again" on at least two key issues – the position of EU nationals living in Britain and a final parliamentary "assessment" once a deal had been struck with Brussels.
Theresa May wants to trigger Article 50 by the end of March
If the elected house has decided not to do so, then the unelected house could not, would not and should not do so
Should peers agree on those amendments, the Bill would be sent back to the Commons – potentially threatening Prime Minister Theresa May's March deadline for formal Brexit talks to be triggered.
There was an additional complication, Lord Lisvane said, given the two year-time frame for negotiations to conclude and the need for a final Parliamentary vote.
"If the clock starts and we have two years to negotiate an Article 50 withdrawal, then that clock carries on winding down to zero," he said.
"If the vote in both houses is very late in that time… if the vote is no then what do you do?
"Do you end up with a nullity? Do you go back to WTO (World Trade Organisation) rules?
"That's a bit of a Catch-22. It may rob that final vote of real significance."
The House of Lords will debate the Brexit Bill for two days, starting on Monday.