Fans celebrating Wales' Grand Slam victory

First Minister Rhodri Morgan said there was there was "no question" that there would be an official event.

It follows a weekend of celebrations after the team's success, which was sealed with Saturday's 32-20 win over Ireland in Cardiff.

The Royal Mint has also confirmed it will produce a commemorative coin.

"We have to have an official celebration - there is no question of that," said Mr Morgan.

"We couldn't make anything than the most tentative plans for having an open-top bus victory parade before the game in case anything went wrong with the result during the game."

Thousands of fans thronged the streets of Cardiff

He said the police would need two to three weeks notice to organised street closures, but talks would now begin in earnest.

"We have got to get onto that at 100mph - at Shane Williams pace - with the police, Cardiff county council and the WRU," he said.

He added that the issue now was whether to concentrate on one big event in Cardiff or a series of events across south Wales.

He also said the Grand Slam had not only won back self-respect on the pitch, but was good for the promotion of Welsh exports.

WRU chairman David Pickering said the win had been "a real Team Wales effort", and they would be sitting down to discuss the celebrations with Mr Morgan.

"It is fantastic to hear the First Minister talking about how important it is for Wales, not just on the rugby field, but in terms of the economy of Wales," he said.

On Saturday, Wales' defeat of Ireland won them the Six Nations Grand Slam and the Triple Crown.

But nine of Saturday's starting line-up of 15 had not even been born by the 1978 Grand Slam.

Wales lifted the Six Nations trophy on Saturday in Cardiff

Sending his congratulations to the team, the Prince of Wales said: "I knew you would do it, one thousand congratulations and many admiring wishes on such a spectacular Welsh triumph - llongyfarchiadau (congratulations in Welsh)."

A full house of 74,000 witnesses Wales' win inside the Millennium Stadium in Cardiff, with a police estimate of a further 200,000 people watching on television screens in pubs and bars throughout Cardiff city centre.

A crowd of between 15,000 and 20,000 also watched a big screen set up on the lawn outside City Hall in the early spring sunshine.

Chief Superintendent Bob Evans, of South Wales Police, said: "There was a great atmosphere and we only had a couple of casualties during the match period, with a few people being treated for having had a bit too much to drink.

"The evening was very busy for officers but only on a par with an average New Year's Eve or match day."