The union will not be recommending that members accept the offer, but does say it is the best that can be achieved through negotiations.

In meetings with management, Prospect and the other unions in TfL made the case for:

• an above-inflation pay increase for all members
• increases in the top of the pay zones and maxima within pay ranges
• parity in the pay awards offered to different parts of the TfL family, in particular between London Underground and the rest of TfL.

But TfL said that because of current financial challenges, the maximum it could afford was:

• a budget of 1% for pay awards for pay bands two and three
• a 1% increase for Band 1 staff below the maximum
• a £500 pay increase for those earning less than £24,500
• no increase to any of the pay range zones or maxima.

Prospect negotiator Nick Radiven said: “We are very disappointed that yet again, TfL is offering staff a pay award well below inflation.

“We acknowledge that TfL has to operate under certain financial constraints, but we believe funding could have been found to offer a higher pay award – not least to recognise staff efforts to deliver TfL’s transformation programme.

“The offer is also well below the one made by London Underground. It is not acceptable that one part of TfL should receive a much higher pay award than another part.”

The ballot will close at 10am on Friday 20 September.