This rise was on the back of a 12.7 per cent rise in revenues during the fourth quarter, according to figures from the Radio Advertising Bureau.
Total radio ad expenditure rose to £601 million during 2003. The fourth quarter increase was the largest since the end of 2000.
The growth was driven by leading FMCG advertisers such as Procter & Gamble and Unilever, both of which doubled their radio spend during 2003.
COI Communications remained the UK's biggest radio spender, increasing its radio budget by just under £5 million to £27.5 million.
P&G was the second-highest spender, adding close to £6 million to its budget and spending £11.6 million.
The top 20 media agencies increased their radio spend by 14 per cent last year and the top 20 radio creative agencies recorded an 11 per cent rise.
Abbott Mead Vickers BBDO remained the highest radio spender, despite cutting its budget by £5 million to £22.7 million.
J. Walter Thompson posted a significant rise in its radio spend from £12.4 million to £18.6 million.
The third-placed agency, Leo Burnett, also increased its radio spend.
Michael O'Brien, the client sales director at the RAB, said: "Radio is leading the way out of the downturn as marketers increasingly turn to radio, attracted by its effectiveness at building awareness and driving sales."