Media playback is unsupported on your device Media caption Janet Ryder, Brynle Williams and Eleanor Burnham all became AMs in 2003, despite losing in Clwyd West

A ban on Welsh assembly candidates standing for election in constituencies and on their parties' regional lists will be lifted, the UK government says.

It also announced that it wants assembly elections to be held every five years instead of four.

However, separate proposals to re-draw the boundaries of assembly constituencies have been dropped.

Welsh Secretary David Jones said the Westminster coalition wanted a "fairer and more transparent" political system.

Of the 60 AMs, 40 represent constituency seats and 20 are elected from five regional lists.

The government has worked to make our political system fairer and more transparent David Jones, Welsh Secretary

Since the 2007 elections, a ban on so-called dual candidacy has barred candidates from standing in both contests at the same election.

The dual candidacy ban was strongly opposed by other parties when it was introduced by the last UK Labour government.

When he introduced the ban, then Welsh Secretary Peter Hain said it was an "abuse" of the system to allow candidates to get elected on regional lists when they had lost first-past-the-post contests in constituency elections.

The ban has resulted in some assembly members losing their seats without being able to rely on the insurance policy of standing in both categories.

After consulting on changes to the assembly's voting system, the UK government said it would scrap the ban "to avoid a disproportionate impact on smaller political parties".

In other changes, politicians will be prevented from sitting simultaneously as MPs and AMs, and the period between assembly elections will be permanently extended to five years.

'Strengthen' assembly

The next assembly election has already been postponed until 2016, extending the current term to five years, to avoid a clash with the next UK general election.

The changes follow a consultation on a green paper, launched by the UK government in May last year.

Media playback is unsupported on your device Media caption BBC Wales political editor Betsan Powys explains the reasons for the changes

The Wales Office confirmed that a proposal in the green paper to re-draw constituency boundaries has been abandoned.

It follows a vote in the House of Commons in January to block a review of parliamentary boundaries before 2015.

Since the outset of devolution, assembly seats have shared the same boundaries as Welsh parliamentary constituencies.

Mr Jones said: "Since coming to power in 2010, the government has worked to make our political system fairer and more transparent.

"This consultation gave people in Wales the opportunity to express their views on possible developments for the systems in place in Wales, and I welcome the contributions that have been made.

"These changes will allow us to further strengthen the National Assembly for Wales, and the government will bring forward legislation to effect these changes at the earliest opportunity."

Responding to the Wales Office decision, Labour said it banned dual candidacy in the 2006 Government of Wales Act "to ensure that the voice of Welsh voters could not be subverted and losing candidates elected by the back door".

A Welsh Labour spokesman said: "The fact remains that these are changes to the national assembly, which the assembly itself has not asked for.

"Welsh Labour will discuss with members and stakeholders the implications these changes pose over the coming days."

Plaid welcomed the "overdue" removal of the dual candidacy ban, as did the Welsh Liberal Democrats.

Both parties said the ban was an attempt by Labour to "gerrymander" assembly elections.