The result is due on February 15 – meaning the first walkouts could start in early March.
Aslef’s strike threat marks a dramatic escalation in the row over pensions and TfL’s bid to make efficiency savings by changing working practices and not replacing departing staff.
The RMT last year held six one-day strikes, most recently on November 10, over the same issues, which include the loss of 600 station staff posts.
It came as TfL confirmed the central section of the Elizabeth line – between Paddington and Abbey Wood – would close on Thursday due to a strike over pay by dozens of line managers in the TSSA union.
This is the first strike by staff working on the Elizabeth line since it opened last May. TfL said a reduced service would operate on its eastern and western branches.
Mayor Sadiq Khan, as part of TfL’s covid bailouts, has been ordered by the Government to set out by the end of January his preferred options to save up to £100m a year on the cost of running TfL’s pension scheme.
No formal proposals for change have yet been made and the mayor’s budget for 2023/24 does not assume any savings will be made. It has also been confirmed that an Act of Parliament would be required to change the TfL pension scheme.
But unions remain concerned about the potential loss of pension benefits and insist any changes to working practices – such as which depots drivers start work and their shift times – must be made in agreement and not imposed upon staff.
Finn Brennan, Aslef district organiser for London, told the Standard: “This week Aslef will give the legally required notice that we intend to ballot our members on London Underground for strikes.
“Our dispute is over management’s failure to give us the assurances we have asked for that any changes to terms and conditions and pension arrangements for our members will only be made by agreement.
“We have repeatedly said that we are prepared to negotiate on changes and work with the company to find ways to cut costs, but we cannot accept cuts to pensions or increases to workloads being forced through without agreement.
“TfL and the Government are due to announce the details of their pension proposal by the end of this month. Our members have been very clear that they will not stand passively by while the income they expect in retirement is drastically slashed.
“Using the buzz words of ‘flexibility’ and ‘modernisation’, [London Underground] want to make huge cuts to staff numbers and increase the workload of those remaining at the same time as removing the agreed procedures on discipline and attendance management.
“Unless management accept that change needs to come by agreement and bring benefits to staff, not just cost savings, then we will see hard hitting and protracted strikes this spring that will bring the tube to a standstill.”
It is understood that the ballot is necessary under trade union laws to allow the union to retain its ability to take strike action - it has had a “rolling mandate” from members for the last two-and-a-half years.
A TfL spokesperson said: “We are aware that ASlef intends to ballot London Underground staff. We continue to work with all our unions following the financial conditions placed on TfL by the Government following the pandemic.”
A TSSA spokeswoman said there was likely to be a “severe impact” when dozens of traffic managers, service infrastructure managers and incident response managers, whose jobs are “safety critical”, walk out on Thursday.
The action - which will also include RMT and Prospect members working on the Elizabeth line - will be followed by a “work to rule” until the end of February in a bid to win pay parity with workers on other parts of the Elizabeth line, which is due to generate £550m for TfL in 2023/24.
TfL confirmed on Monday that the Elizabeth line would be shut throughout Thursday between Paddington and Abbey Wood.
Services between Paddington, Heathrow and Reading on its western branch, and between Liverpool and Shenfield on its eastern branch, will be reduced, with the possibility of “short-notice alterations or cancellations”.
In the west, the line will be limited to two trains per hour from Paddington to Reading, two per hour from Paddington to Maidenhead and two per hour from Paddington to Heathrow Terminal 4, There will be no services to Terminal 5.
There will be a Saturday service in and out of Liverpool Street station, with the possibility of extra services at peak times.
Separately, the RMT and Aslef were on Monday due to meet rail minister Huw Merriman in a bid to secure a breakthrough in the national rail dispute.
No new strikes have been announced by either union in their bid to secure pay rises without a threat to working conditions. Passengers were hit by five consecutive days of strikes last week that ended on Sunday morning.
This morning, signal problems at Waterloo meant delays on South Western Railway passengers. Southeastern reported problems at Charing Cross station due to Network Rail electricity supply problems.