Senedd Member Sarah Cooper-Lesadd Defects To Plaid Cymru, Says She Would Back Welsh Independence

Sarah Cooper-Lesadd, a member of the Senedd elected as a Reform UK representative, has left the party and joined Plaid Cymru, saying she would vote for Welsh independence if a referendum were held and revealing she voted Remain in the 2016 EU referendum.

Her defection was announced on the same day Reform's Wales leader Dan Thomas stepped down following an arrest on suspicion of assault. The move increases Plaid Cymru's representation in Cardiff Bay to 44 members while Reform — still the largest opposition grouping after the election — now holds 33 seats.

Why She Left Reform

Cooper-Lesadd told the BBC's Walescast she had reached her decision after "a period of deliberation" and described her change of allegiance as the result of a journey rather than an impulsive move. She criticised Reform as "completely chaotic" and said the party was "falling apart at the seams."

"Joe Martin's comments about Sudanese asylum seekers just completely did not chime with the type of person that I am and the values that I have," she said, describing the June speech as one of several "flashpoints."

Cooper-Lesadd, a former Conservative, was elected in May as the Reform MS for the Pen-y-bont Bro Morgannwg constituency. Her switch to Plaid means she has been affiliated with three different parties since 2024. She said she had become uncomfortable with the language and tone used by some Reform members and felt Plaid's values aligned better with her own.

Constitutional Views And Brexit

On the constitutional question central to Plaid's platform, Cooper-Lesadd said she supports self-determination and would vote "yes" in a referendum on Welsh independence, adding: "Wales is short-changed in so many different ways, but we aren't there yet. The nation is on a political journey, and I'm on a political journey as well."

She also revealed she had voted Remain in the 2016 EU referendum and said Brexit had damaged trading relationships. "I've never, ever spoken about Brexit, and I'll be honest I voted remain... In the public discourse over the last 10 years, we haven't been able to have that debate about the European Union," she said.

Constituency Work And Party Response

Under current Senedd rules, members who change party affiliation are not required to trigger a by-election. Cooper-Lesadd stressed she would continue to represent and fight for her constituents: "My work with my constituents doesn't end today — I'll continue standing up for them and working extremely hard."

Reform MS Llyr Powell told BBC Radio Wales Breakfast that the party had made significant efforts to engage with Cooper-Lesadd before her decision. He questioned whether she had fully understood the core values she campaigned on and expressed scepticism about the explanations for her defection.

What This Means: The defection shifts the balance of party numbers in the Senedd and highlights continuing tensions within Reform UK after the May election. It also adds a senior voice to Plaid's ranks who publicly supports both greater powers for Wales and, ultimately, independence.