The Conservatives accused Labour ministers of deliberately inflating the budget in the run-up to the general election expected next May. But COI Communications insisted the increase was because of it winning new business.
In the financial year, which ended in March, COI spent £167.6 million on media advertising and £21.9 million on production costs. In the previous 12 months, the figures were £134.8 million and £25.9 million respectively.
COI's annual report, published this week, showed that its total ad budget jumped from £258.4 million to £307.6 million as the organisation expanded its PR and sponsorship, direct and relationship marketing and research work.
A Tory source said: "We are not surprised by the increase. It is part of a pattern and the same thing happened in the build-up to the 2001 election."
The Tories called on the National Audit Office, the public spending watchdog, to investigate whether higher spending delivered value for money.
COI bosses insisted there was no significant increase in spending by its principal clients in government departments. Peter Buchanan, the COI deputy chief executive, said: "We had a successful period, gaining new business in less traditional areas. This reflects COI's wish to attract the widest selection of public-sector business even though our core clients are still the main government clients."
He cited the £5 million media spend channelled through COI by the British Heart Foundation and Cancer Research, the £3.5 million Visit Britain tourism campaign by WCRS and a £3.3 million spend by the Electoral Commission, mainly by St Luke's.
COI's annual report no longer gives a breakdown of what individual departments spend. Those that increased their adspend in 2003-04 include the Department for Work and Pensions.
The report says COI's bulk-purchasing discounts won a 40 per cent discount for clients against industry benchmarks and won a record 8.63 out of ten client-satisfaction rating.
This article was first published on Campaign