A PLAID Cymru AM who represents the mid and west Wales region in the Senedd has been arrested on suspicion of possessing indecent images.

Simon Thomas AM resigned abruptly from his political office today, following news that police were undertaking an investigation into a serious offence.

A Dyfed-Powys Police spokesperson said: "An individual from Aberystwyth has been arrested on suspicion of possessing indecent images.

"The individual has been released on police bail for 28 days."

The 54-year-old father of two from Aberystwyth was elected to the Senedd in 2011, and was previously MP for Ceredigion between 2000 and 2005.

Plaid Cymru's chair Alun Ffred Jones said the party was aware of the resignation but felt it was innappropriate to comment due to the ongoing investigation.

Plaid Cymru confirmed they had accepted Mr Thomas' resignation after being made aware of the police investigation.

In a statement, the Senedd's presiding officer, Elin Jones said:"The Llywydd has received a letter of resignation from Simon Thomas with immediate effect."

Mr Thomas resignation from the Senedd will not trigger a by-election as he came to office via the mid and west Wales regional list.

The next Plaid candidate on the list is former AM Helen Mary Jones, who must now decide whether or not she wants to replace Mr Thomas.

In a tweet, she said: "In something of a state of shock. I have now got some big decisions to make in the next few days. I won't be on here a lot. Thanks for good wishes already recieved [sic]."

Mr Thomas, who lives in Aberystwyth, has deleted his Twitter page and personal website.