The Lords are due to look at the details of the bill in the New Year with threats of ‘trench warfare’ from Remain supporters.
In anticipation of a delay to the Government’s plans of implementing Brexit, the Lords authorities have increased the estimated number of days the House will be required to sit.
Most members of the House of Lords do not receive a salary and instead can claim a £300 allowance for every day they attend the House. In addition to this allowance peers can claim expenses, such as travel costs.
The Lords authorities have planned for 140 sitting days in the 2018-2019 financial year. However, this prediction is likely to be increased as the House prepares to examine the EU Withdrawal Bill.
The authorities are now anticipating 145 sitting days, with an average of 500 peers expected to attend.
The additional cost of the extra five sitting days for 500 peers could be £750,000 in allowances alone.
When adding travel and other costs to this amount, it is likely the figure will £1m.
Labour’s former Transport Secretary Lord Adonis revealed his contempt for Brexit following the Government’s first defeat on the Brexit Bill last week.
He wrote on Twitter: “First step towards defeat of Brexit. And this is before the Lords has got going on the National Betrayal Bill.”
The Conservatives have the most members in the House of Lords but are not close to having a majority. There are 200 Tory peers, 194 Labour, 96 Lib Dems, 152 cross-benchers, 24 bishops and other non-affiliated members.
There are rumours new Conservative peers could be nominated by Theresa May in the New Year.
In anticipation of a tough fight from anti-Brexit peers the move would be seen as a bid to strengthen her authority in the Lords.
A House of Lords spokesman said the Government was responsible for setting out the business schedule.
They said: “These are the administration’s assumptions rather than being based upon any information provided by Government.
“The number of sitting days is unknown at this time and is dependent on the progress of business.”