Harry Redknapp wants the FA Cup Final between Portsmouth and Cardiff City today to be remembered as the day when respect returned to football.

Redknapp hopes that supporters at this afternoon's final can return to the tradition of staying for the trophy presentation - win or lose. However, the Portsmouth manager's nostalgic call comes amid concerns that Cardiff supporters could boo the National Anthem in front of a television audience of 500 million in 169 countries.

“I just hope the fans, at the end of the game, stay and watch the winning team get the FA Cup, whether it is Cardiff or Portsmouth,” he said.

Redknapp was dismayed after watching Chelsea beat Manchester United last year. “I couldn't believe it,” he said. “Suddenly half the supporters had left. They couldn't bear to see the other team lift the cup.

“I'm hoping that this time all the supporters will stay there and think, 'It's been a fantastic run, a great day,' give both teams a good ovation and stay and watch the cup be presented.

“It's society, isn't it. But as a football person, a football fan, I find it strange to understand.”

Calls for harmony were endorsed by the Cardiff director, Steve Borley, as Katherine Jenkins prepared last night to become the first person to sing the Welsh National Anthem, Mae Hen Wlad Fy Nhadau, at an FA Cup Final. “The English FA has paid us an enormous amount of respect by permitting us to play and sing our anthem at the home of English football,” Borley said.

He urged the 25,000 travelling Cardiff supporters: “Please soak up the atmosphere, take an active part in the traditional ceremony before the game and savour the day. After the whistle blows, let's show the world that we can make some noise, support the boys and take part in the normal banter in a day to remember in the life of a City fan.”

The issue is being debated among Cardiff fans on the internet. One chat room fan said: “I know the majority of us have a hatred of God Save the Queen and I am no exception, but all of us lucky enough to be going to Wembley should 'respect' their anthem. If we must show our feelings, simply turn our backs and greet it with silence, that's what I will do.

“To shout it down will paint us in a bad light in front of millions of people, many of which do not know Wales is a country, let alone that there is a Cardiff City.”

Approximately 1,200 police officers will be on duty in and around Wembley for a match that Redknapp insists will not be his last in charge of Portsmouth, despite speculation that he could announce his retirement.

A win today would allow him to plan for a Uefa Cup campaign and the money brought in by the Cup run should ensure that he will not be forced to sell before he can strengthen the team this summer. In January he had to finance the capture of Jermain Defoe from Tottenham Hotspur with the sale of Benjani Mwaruwari to Manchester City.

For Cardiff, too, the final will bring some respite from serious financial pressures. The semi-final victory over Barnsley took the Coca-Cola Championship club's total of FA prize-money so far to £900,000 and a win today would lift that figure to £1 million. A further £1 million is expected from broadcast and gate revenues.

CommsDirect, Cardiff's shirt sponsor, has also turned down an offer of £500,000 from an Asian-based online gambling firm to give up its advertising rights for the final.

Peter Ridsdale, the Cardiff chairman, believes that a deal is close to being struck with Sam Hammam, the former owner, who claims that he is owed £24 million. “I am in dialogue with Hammam,” Ridsdale said. “We are pretty close to deciding how it will be resolved.”

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