REGIONAL Rugby Wales (RRW) has launched a scathing attack on the Welsh Rugby Union (WRU) as the bitter battle between the two sides shows no sign of abating.

RRW - the umbrella organisation which represents the Ospreys, Scarlets, Newport Gwent Dragons and Cardiff Blues - made it clear the regions could not sign an extension to a Participation Agreement with the WRU prior to Tuesday's deadline.

The decision was due to the Union being unable to guarantee critical areas such as revenue and competition structure given the ongoing uncertainty of the Heineken Cup.

The regions want the WRU to back their support for the Rugby Champions Cup (RCC) next season, a breakaway European competition initially put forward by the English and French clubs as an alternative to a Heineken Cup under the auspices of European Rugby Cup (ERC).

RRW gave the Union a January 31 deadline to support it or it would ''pursue further competition options''.

The Union's response had been to suggest it could form new professional teams in Wales, but on Thursday it said it was prepared to offer the regions a new deal, which is expected to be put forward on Monday.

However, the Union has since sent a letter to its 320 member clubs on the impasse regarding the Participation Agreement.

It is understood to re-affirm the Union's backing to ERC and suggests leaving their Irish, Scottish and Italian counterparts in the lurch would weaken the Six Nations.

The letter also made it clear the WRU will not give its blessing to an Anglo-Welsh league, which the regions are expected to pursue fully if no agreement is reached by the end of this month.

RRW's statement makes clear its desire to see the regions play in the RCC, stating any ERC tournament would be "an inferior competition".

It also accuses the WRU of "failing miserably" to secure revenue distribution on a par with clubs in England and France, and launching "vitriolic and disingenuous" attacks on the regions.

The RRW statement read: "The Rugby Champions Cup will bring the biggest increase of funding into the Welsh game in five years. It will increase funding to the Irish clubs and protect the Scottish clubs.

"Bringing in £12million in three years into the Welsh game does not threaten the Six Nations or bring about its demise.

"In only two months, the Welsh Regions have themselves, negotiated the biggest increase in funding for Welsh Rugby of the last five years and are simply asking the WRU as the governing body for support in this.

"The WRU not only has full responsibility, but is also contractually obliged to negotiate competition revenues and TV distribution revenues under the Participation Agreement.

"The WRU has failed miserably to negotiate equitable and fair revenue distribution for Welsh clubs in line with clubs in England and France."

It continued: "The ERC Accord finishes this year and the WRU's latest proposal for a replacement to exclude the English clubs includes six undefined French clubs and maintains an unequal distribution of revenue to the Welsh clubs.

"Given the other opportunities that now exist, it is an inferior competition. The proposed competition would only be available on Sky TV, not terrestrial television, as is the case with the existing European competition."

On the matter of forming an Anglo-Welsh competition with the 12 Aviva Premiership clubs, RRW added: "The Regions would question why the WRU are scaremongering about a break away.

"This has never been mentioned by the Regions who have only asked for positive support as outlined in their most recent statement of December 31.

"As stated then; it continues to be the absolute intent and strong desire of RRW and the Regions to work with the WRU in progressing such a positive position for the next five years of professional Rugby in Wales, or indeed to discuss any proposals WRU themselves may have that could provide an even stronger platform for sustainable and competitive professional rugby across Wales.

"It is incredulous to the Welsh Regions that the WRU refused to discuss any item in the current Participation Agreement before its deadline of 31st December but is now willing to offer a "new agreement" on different terms.

"Equally it is yet to be explained by the WRU why bringing an additional £12million into the game by the Regions, is not in the best interests of Welsh rugby."