Image copyright Getty Images Image caption The Welsh Assembly will be called Senedd Cymru/Welsh Parliament from May

It has been suggested Wales could face political turmoil after next year's Senedd election, in light of the annual St David's Day poll for BBC Wales.

The poll suggests three parties could win similar numbers of seats - Labour 21, the Tories 20 and Plaid Cymru 18.

The research, by ICM Unlimited, now includes 16 and 17-year-olds, who will vote in 2021 for the first time.

The poll also suggests increased support for independence, up to 11% from 7% last year.

Support for abolishing the assembly shows little change compared to last year and stands at 14% - up one percentage point from last year.

ICM says there is a caveat to this poll in the fact that there is a different sample to previous years, in that 16 and 17-year-olds have been included in the questioning.

From 2021, under new legislation, 16 and 17-year-olds will have the right to vote in Senedd elections for the first time.

On next year's Senedd elections, on the constituency vote, Labour and the Conservatives each poll at 31%, Plaid Cymru and 26% and the Liberal Democrats at 6%.

On the regional vote , Labour poll at 31%, the Conservatives at 29%, Plaid Cymru at 25% and the Liberal Democrats at 5%.

Prof Roger Awan-Scully, Head of Politics and International Relations at Cardiff University, has made the following projections based on a uniform national swing since the 2016 Senedd election: Labour 21 seats, Conservatives 20, Plaid Cymru 18 and the Liberal Democrats 1.

Commenting on the poll, Vaughan Roderick, the Welsh Affairs editor at BBC Wales, said: "Opinion polls are snapshots not predictions but Wales could be facing a period of unprecedented political turmoil if the three-way political split between Labour, the Conservatives and Plaid Cymru continues into next year.

"It is difficult to see what kind of government might emerge from an assembly where all three parties had roughly equal number of seats.

"Plaid Cymru would be unlikely to support a newly-humbled Labour Party while supporting a Conservative-led administration would be all but politically impossible for both Labour and Plaid.

"In such circumstances the assembly might even be forced to vote to dissolve itself and hold a fresh election in an attempt to resolve the impasse."

He added: "It's important to note that this poll includes 16 and 17-year-olds in the sample, as they will be allowed to vote in the 2021 Senedd elections for the first time ever."

Mr Awan-Scully said: "My projections come with the usual health warnings and exceptions.

"On this polling, and using a uniform national swing, Labour could just about hold onto Clwyd South but could lose the Vale of Glamorgan, Vale of Clwyd, Gower, Wrexham and Cardiff North to the Conservatives.

"Labour could also lose Llanelli, Blaenau Gwent, Cardiff West and Caerphilly, on the same basis, but local conditions could impact on this."

Support for Welsh independence hits a nine-year high, with 11% saying they think "Wales should become independent, separate from the UK" - which is up four points compared to 2019.

ICM say a caveat here should be the changed sample definition of including 16 and 17-year-olds, with a greater proportion of younger people than older people who say they support independence.

Despite the increase in support for independence, the most common response continues to be that the "Welsh Assembly should have more powers than it currently has", which is at 43%, down three points from last year.

Support for abolishing the Welsh Assembly remains consistent with last year at 14%.

Vaughan Roderick said: "The uptick in support for independence to a nine-year high isn't insignificant but it's worth noting that supporters of independence are still outnumbered by those who'd like to see the assembly abolished entirely.

"A large majority of respondents though supported either the current settlement or increased powers for the Senedd, a finding that has remained remarkably consistent over the past two decades."