Nye Bevan is the current leader of the poll

Assembly Culture Committee Member Leighton Andrews said he was "gobsmacked" to learn that Robin Gwyn, Director of Communications at the National Museum, was urging people to vote for Owain Glyndwr to oust the founder of the NHS from the lead.

The National Museum is one of the member organisations of Culturenet Cymru, which is running the poll due to be announced on St David's Day.

Mr Andrews said it called into question the integrity of the ballot - an accusation strongly rebutted by Culturenet Cymru.

It is vitally important that everybody uses their networks of members/contacts/family/friends to get Owain back on top urgently! Robin Gwyn's e-mail

Mr Andrews added: "I've also heard from people who couldn't vote for Aneurin Bevan earlier in the week because the system wasn't working.

"I can understand why people might want to get their friends to vote for a particular hero. It's not a hanging offence - this whole contest is a bit of fun.

"But if people want to get their friends to vote they should do so from their home e-mails. I'm not actually sure that members of organisations promoting the contest should be voting at all."

Wales' 15th Century rebel leader, Owain Glyndwr

Mr Gwyn told BBC Wales News Online he had sent e-mails in Welsh from both home and work to a "fairly close-knit group of colleagues, friends and relatives" numbering perhaps 40 or 50.

He said he was expressing a personal opinion, and "certainly not the official view of the National Museums and Galleries of Wales".

He said the competition had been trying to encourage people to access culture online.

"As far as I know, people working for the organisations involving in the consortium were not proscribed from voting."

Mr Gwyn said: "It's a harmless bit of fun." He said the only thing he regretted was if he had caused confusion in relation to the museum.

He said Owain Glyndwr was a "personal hero - a historical figure who did a lot for Wales."

Leighton Andrews: E-mail 'calls into question' ballot's integrity

One of his e-mails, in translation, read: "As you can see, Aneurin Bevan is in the lead once again - and only three days to go.

"It is vitally important that everybody uses their networks of members/contacts/family/friends to get Owain back on top urgently!"

Culturenet Cymru said that it has complete faith in the integrity of voting for its "100 Welsh Heroes" project.

Chair of Culturenet Cymru Andrew Green added: "We have taken every technical precaution possible to eliminate bogus email based votes. These votes are controlled by an email/password combination.

"To vote on the website you must register with a valid email address. This address is validated by a password. The email address is the unique identifier for any registered web user. Any particular email address can be registered only once. Registered users are informed, when they vote, that they will be able to vote again in 7 days time. If they try to vote beforehand, the vote is not counted."

The online contest is due to close on 23 February, with the 100-strong list announced on St David's Day, 1 March.

On Friday, Aneurin Bevan, the politician responsible for founding the NHS, was leading the 15th Century rebel leader Owain Glyndwr by 1863 votes to 1727.

Others in the top 10 include singer Tom Jones, politicians Gwynfor Evans and David Lloyd George, actor Richard Burton and poet and playwright Dylan Thomas.

The highest woman on the list is actress Catherine Zeta Jones, currently at number 16.