Two senior Labour figures have clashed over whether Welsh voters would be better off inside or outside the EU.
Labour MP Gisela Stuart, chair of the Vote Leave campaign, said her party should "stand with the working people of Wales" who would be better off outside the EU.
But former Welsh Secretary Lord Hain said Ms Stuart, who represents Birmingham Edgbaston, had "no right to claim to speak for voters in Wales".
The referendum takes place on 23 June.
Labour's official position is to support the remain side, but some of the party's MPs are campaigning to leave.
Ms Stuart told the Western Mail newspaper: "Big corporations make up just 1% of all businesses in the UK. In contrast small businesses employ over 15 million people in Britain and there are thousands of people in Wales alone who rely on those businesses being able to grow and take on more staff.
"By giving up control of the laws that govern us to people we have not elected, cannot get rid of and who run things in a way that too often benefits the big corporations, we are unable to support working people in the way that I know a Labour government can do."
Later Ms Stuart told BBC Wales that the fact no Welsh Labour AMs or MPs are campaigning to leave the EU shows the party has "a very good whip".
But Lord Hain said: "Gisela has no right to claim to speak for voters in Wales when every Labour MP and every Labour AM in our country have come together to say Wales is stronger, safer and better off in Europe.
"The Labour government in Wales is committed to a future of fairness and opportunity - our membership of the European Union is a key factor in delivering this.
"The MP for Birmingham Edgbaston would do well to familiarise herself with the realities of Welsh life before attempting another intervention."
A Welsh Labour spokesman said: "Welsh Labour are totally united in supporting a Remain vote on 23 June which is why Gisela's visit was organised by Tory staff."