A REFERENDUM on changing the Westminster voting system could be held on the same day as next May's Assembly elections, it was reported today.

A date for the referendum on voting reform will be announced next week, with the BBC reporting the UK Government had chosen May 5, 2011 - the day scheduled for devolved elections in Wales and Scotland and local elections in England.

With a referendum to give the Assembly primary law-making powers also due early next year, it means Welsh voters could visit the ballot box three times in the spring.

There are calls to delay the Assembly election so campaigning does not clash with the law-making referendum, expected to be held in March.

Assembly opposition and Welsh Tory leader Nick Bourne this week said party leaders in Cardiff Bay agreed the election should be postponed by four weeks to allow more time.

A referendum on switching from first-past-the-post to the alternative vote system in general elections was a key Liberal Democrat demand when forming the coalition with the Tories.

A Welsh Conservative spokesman said: "Nick Bourne intends to raise this issue when he meets the Secretary of State on Monday.

"Earlier this week he wrote to Carwyn Jones, Ieuan Wyn Jones and Kirsty Williams seeking their support for the Assembly elections to be delayed for a month because of the likely Assembly powers referendum campaign next spring.

"He believes the First Minister needs to make that request to the Secretary of State as soon as possible and before any costs are incurred in relation to a May Assembly election.’’