Prospect and sister union the FDA have agreed to give contingent authority to ballot on industrial action this autumn if the Government does not amend its proposal to impose a pensions levy on civil servants from April 2012.

Talks with the Treasury continue but Prospect, representing 36,000 professionals and specialists, and the FDA, representing 18,000 senior public servants, have made it clear that balloting will begin unless progress is made soon.

Both unions will work closely through the TUC with other public sector unions.

In a joint statement, Paul Noon, Prospect General Secretary and Jonathan Baume, FDA General Secretary, said: "We continue to seek every opportunity to engage in negotiations. However, we believe that pension reform cannot be separated from the overall reward package, and must be considered alongside reform of civil service pay arrangements. Unfortunately, the Government seems unwilling to consider these issues as a whole and engage constructively.

"The imposition of an increase in pension contributions from April 2012 is simply a tax on civil servants and other public sector workers, and has nothing to do with the sustainability of their pension schemes. We recognise that the UK faces a fiscal deficit, but our members are being asked to pay too high a price for the failings of others, at a time of high inflation and a two-year pay freeze."

Both unions have urged the government to listen to its members' responses to its consultation on the issue, and reconsider its approach.

"If this message falls on deaf ears we are left with no option but to ask our members to demonstrate their strength of feeling through industrial action, probably later in the autumn," they said.

Their comments in a joint news release were reported widely, including on the BBC website, the Today programme, Radio 5 Live, Guardian Professional  and Daily Mail.