Tom Ellis was born in Pant near Rhosllannerchrugog and was educated at Ruabon Grammar during the 1930s. He had a career in the mining industry, being appointed manager of the Bersham Colliery in 1957. He took further studies at the University of Wales and at Nottingham and later became president of the Wrexham Fabian Society.

Ellis first stood for Parliament – without success – in Flint West in 1966. He won his seat at the next election becoming the new Labour MP for Wrexham. He was re-elected in both elections in 1974 and in May 1979. He also served as an indirectly elected MEP from 1975 to 1979.

Ellis had grown increasingly disaffected with the leftward direction of the Labour Party by the beginning of the 1980s. He was one of the handful of Labour MPs loyal to Roy Jenkins prepared to leave the Labour Party even without the famous ‘Gang of Three’. Ellis had even gone so far as seriously to contemplate joining the then Liberal party under David Steel. Ellis’ disenchantment with the Labour Party was so great that he probably voted for Michael Foot over the much more centrist Denis Healey in Labour’s 1980 leadership election – probably in order to accelerate the almost suicidal disintegration of the Labour Party.

In 1981, Ellis did became one of the founding members of the Social Democratic Party, the SDP. He was one of three Welsh MPs to join the new party (the others were Jeffrey Thomas and Ednyfed Hudson Davies) and he was elected to serve as the President of the Welsh Social Democrats. As a result of boundary changes, Ellis did not contest the Wrexham constituency in 1983. Instead he stood for the SDP in the new constituency of Clwyd South West which nevertheless incorporated much of his old constituency. He finished second to the Tory Robert Harvey by 1,551 votes in a competitive three-way race.

Ellis made his home in Whitehurst near Chirk and all three of his sons attended Ysgol Dinas Bran.