Career
At the 1923 general election, he was an unsuccessful candidate in Southampton, coming fourth in the two-seat constituency. He stood again in the 1934 Lowestoft by-election, losing by 1,920 votes to the Conservative candidate, Pierse Loftus. Sorensen was elected as Member of Parliament for Leyton West at the 1929 general election, defeating the sitting Conservative Member of Parliament James Cassels by a majority of 2,153.
When Labour split at the 1931 general election, Sir Wilfrid Sugden retook the seat for the Conservatives with a majority of nearly 10,000.
At the Labour Party Congress in Hastings in 1933, Sorensen emerged as a major critic of the harsh means by which the British rulers were striving to maintain their empire in India. "We are appalled by what is happening to the Jews in Germany, but what has been happening in India is just as bad."
Sorensen narrowly regained the seat at the 1935 election, and represented the constituency until it was abolished in 1950.
At the 1950 general election, he was returned to Parliament for the new Leyton constituency. Sorensen was a committed pacifist.
However, following the outbreak of World War Two, while expressing disappointment at the failure of the peace movement to prevent war, he urged his fellow pacifists "not to obstruct the war effort".
A noted secularist, he became an Appointed Lecturer at the South Place Ethical Society in the 1960s. At the 1964 general election, he was re-elected for a seventh term in the House of Commons. Shortly afterwards, on 15 December 1964, he was created a life peer, as Baron Sorensen, of Leyton in the County of Essex.
He then served until 1968 as a Lord-in-Waiting in the House of Lords.
He had been offered the peerage to make a vacancy for the Foreign Secretary, Patrick Gordon Walker, who had been defeated in his Smethwick constituency.