Former Prime Minister Gordon Brown and Richard Lochhead, the Scottish Rural Affairs minister, reacted angrily as it was revealed after a Dalgety Bay Forum meeting that the clean-up plan for the Fife beauty spot will not begin until the end of May 2013.
It means a stretch of the beach next to the Ross Plantation will remain closed to the public until then.
The Scottish Environment Protection Agency (Sepa) said more investigation is required before clear-up options can be identified amid Ministry of Defence (MoD) claims that it may not be wholly responsible.
Sepa said at yesterday's forum that an investigation plan including "the development of remediation options" has been agreed with the MoD.
But no clear-up will begin before May next year and Mr Brown, MP for Kirkcaldy and Cowdenbeath, said a timetable should already have been agreed.
The contamination is thought to stem from residue of radium-coated instrument panels used on military aircraft which were incinerated and put in land-fill in the area after the Second World War.
Mr Lochhead urged the MoD to "come forward with credible plans to investigate the source of the contamination at Dalgety Bay and clean up the mess".
Sepa earlier called on the MoD to provide a clear-up plan or it would designate the bay as "radioactive contaminated land".
The watchdog has now delayed that move until more information is gathered about the radioactive material.
Such material was first detected on the foreshore of Dalgety Bay in 1990 and more was found last October, prompting the closure of part of the foreshore.