The British singer's tune Congratulations was beaten to the top spot by Spanish entrant Massiel in order to boost the country's international image, a film-maker said.

Sir Cliff's song had been a favourite with the judges during the competition held at the Royal Albert Hall, but lost out on the title by just one point following a last minute rally in votes for Spain.

In a documentary aired on Spanish TV on Sunday night, director Montse Fernandez Vila claimed Spain's win was "bought" by corrupt executives working for state-run television.

Ms Fernandez Vila told Spanish newspaper 20 Minutos that executives travelled round Europe pledging to buy series from other nations to help steer the voting.

She said there was evidence that Franco thought a win would help improve the Spanish regime's international standing.

Despite coming second to Massiel's La La La, Congratulations went on to become a UK number-one hit for Sir Cliff in 1968 and topped the charts in many other countries.

The song stayed at number one in Germany for seven weeks and sold more than one million copies.