Tube drivers earn almost £59,000 a year – meaning they could receive almost £5,000 a year more.
The final year of the four-year deal for about 15,000 station staff and drivers awards them the RPI rate of inflation, as measured in February, plus 0.2 percentage points.
The rise is likely to cost Transport for London £100m – at a time it remains reliant on Government bailouts to keep services running.
The Office for National Statistics on Wednesday announced that RPI last month was 8.2 per cent – meaning an 8.4 per cent rise is on the cards for London Underground workers.
The Mayor has already said that it was important to stick with the terms of the deal, which was struck in 2019, before the pandemic sent prices soaring, to ensure future deals could be struck.
TfL bosses are meeting the Tube unions on Wednesday afternoon at a LU company council to hammer out how and when the increase will be paid.
A TfL spokeswoman said: “In April, we enter the fourth year of the four-year pay agreement covering staff on London Underground contracts.
“This binding agreement was made before anyone could have predicted the pandemic’s effects on our finances or the 30-year high inflationary levels that we are now experiencing.
“As per the agreement, the pay increase for 2022/23 will be based on the RPI figure for February of 8.2 per cent plus 0.2 per cent and we will confirm the plan for implementation with employees in the coming days.”
Aslef, the union that represents most Tube train drivers in London, said: “We are three years into a four year deal and the Mayor of London is doing the right thing by sticking with a deal, agreed in good faith, by both sides.
“[It] means that Tube train drivers who worked throughout the pandemic to keep the capital moving will not suffer a real-term cut in wages as the Government fails to get a grip with the cost of living crisis in this country.”
RMT London regional organiser John Leach said: “Our members have worked tirelessly to keep London Underground running throughout the pandemic and to keep the capital moving as society opens up.
“This four-year deal agreed before the pandemic involved intense negotiations and RMT is simply doing what all unions do, winning the best possible deal for our members.”
A TSSA union spokeswoman said: “Workers everywhere are being hit by the cost-of-living crisis as essential bills for food and energy skyrocket.
“We’re pleased that our London Underground members will get the pay rise that was collectively negotiated by us and other unions several years ago.
“All TfL staff deserve to receive this pay rise, including the many TfL workers who have had years of pay freezes and job cuts. All workers deserve a pay rise which meets the cost-of-living increase.”
Underground staff were given a two per cent pay rise last year when inflation was 1.4 per cent. A clause in the agreement guarantees a minimum increase of two per cent.
The current rate of CPI inflation is 6.2 per cent.
Mr Khan increased Tube and bus fares by 4.8 per cent at the start of March.
A Tube driver’s full-time annual salary is £58,949. Station staff have a broad range of roles and grades but most earn less than this amount.
Lib-Dem assembly member Caroline Pidgeon said: “Whether it is the setting of fares or pay rises it makes no sense to use a baseline of just one month’s rate of inflation. A much better way of setting fares and wages for TfL staff needs to be found.”
Keith Prince, GLA Conservatives transport spokesman, said: “Surely savvy business planning involves factoring in and mitigating risk so that ‘nearly bankrupt’ TfL doesn’t have to accommodate a pay award of 8.4 per cent per London Underground staff member.
“The mayor was advised to put a cap on the RPI figure, but he refused to do so. It’s also a travesty that London continues to be held to ransom by striking workers on a very, very good deal.”