Members at the Gallery will picket outside the main entrance in Trafalgar Square from 8.30am.

The 24-hour strike is the second undertaken by Prospect members this year and follows a campaign of action short of a strike that reflects growing anger at management’s refusal to reopen pay negotiations.

Conservators, curators, information assistants, librarians, information systems staff, photographers and designers at the Gallery are angry that the Treasury was almost 12 months late in agreeing their 2007 pay remit.

As well as being outraged at the imposition of a two-year deal which covers both 2007 and 2008, members are deeply unhappy over the lack of any action to improve progress through pay bands (it currently takes 18 years to reach the top) and the miserly increase to pay band ceilings which will impact on future earnings and result in smaller pensions.

Prospect Negotiations Officer Azim Hajee said: ”Our members acknowledge that this is financially a very rocky time for everyone at present but their grievances go back many years.

“Interference from the Treasury and the Department for Culture, Media and Sport has meant the Gallery’s management were prevented from tabling any offer until March 2008, nearly 12 months late. When it arrived they were tied down over the detail, leaving no scope for negotiations even for the coming year.

“This will be the third year in succession staff have had a below inflation award imposed, and their patience is exhausted.

"The heritage sector has never been known for generous salaries, yet our members have been dealt a double blow at a time when living costs are soaring. Our members deeply regret any inconvenience caused by the action but feel they must take a stand to defend the skills and expertise within the Gallery.”

Prospect represents over 60 members at the National Gallery. The offer imposed for both 2007 and 2008 equates to 3.8% per year. At the due settlement date (April 2007), RPI inflation stood at 4.5% and was 4.8% in August 2008.