The Welsh Rugby Union last night denied claims that Cardiff, Llanelli and Swansea were guaranteed places in a proposed British league - if it becomes a reality.

"Our stance has not wavered. It has always been the top four from our league," said a union spokesman. And he stressed the only way a British league could happen was with the blessing of the WRU, the Rugby Football Union and the Scottish Rugby Union.

Cardiff, Swansea and Llanelli were reported as having accepted an invitation to be part of a British league system they hope will kick off next August.

A fourth Welsh club, was to be nominated by the Welsh Rugby Union, and would join them in the new 16-team tournament next season if it received the go-ahead from the governing bodies.

The RFU is opposed to the plan drawn up by English First Division Rugby chairman Tom Walkinshaw because it does not believe a British league would be any improvement on the Allied Dunbar set-up.

Walkinshaw has proposed a 16-team competition made up of 10 English, four Welsh and two Scottish representatives.

The plans have provoked controversy in Wales and England, with leading clubs accusing those behind the plan of under-mining the Welsh-Scottish League.

The failure of the Heineken Cup and European Shield to consistently attract big crowds outside France has also raised questions about the viability of a British league.

Cardiff chairman Peter Thomas is leading calls for a season-long cross-border competition. He said, "The Welsh-Scottish League does not have a sponsor and is not attracting the crowds. Even if it is expanded into a Celtic league involving Irish sides, I can't see it providing the kind of financial security we need to survive."

But Cenydd Thomas hit back, saying, "We are denigrating our own competition. We should be talking up and improving our own league rather than continually knocking it.

And he called on Walkinshaw and Peter Thomas to provide hard evidence of the £84m five-year television and sponsorship package they claim to have for a British league.

Harris said he was assured by WRU chairman Glanmor Griffiths last Friday that the governing body would reject the plan to issue invitations to Welsh clubs to join a British league and that Llanelli would not back it unless the union did.