It wasn't just Herbert Morrison at the London County Council. Here's
Wikipedia.
'By the late-19th century, Charing Cross was seen as being inconveniently placed. In 1889, the newly formed London County Council's John Burns proposed that the station and its approach should be demolished, with a road bridge put in place. The idea gained support with in the council as it would allow the Strand to be widened and put a road crossing over the Thames that could bypass Whitehall. When the SECR went to Parliament asking for an act to strengthen the bridge in 1916, Burns suggested the station was in the wrong place and should be rebuilt on the south side of the Thames. The following year, an act was passed to reconstruct the bridge, with strict conditions about its appearance and a ban on enlarging the station building itself...
'In 1926, the Royal Commission on Cross River Traffic proposed that Hungerford Bridge should be replaced by a double deck road / rail bridge, and a new Charing Cross station built to the east of the old one. The SR approved the idea as it would allow them to expand the station. Two years later, a proposal appeared again to build just a road bridge and relocate the station south of the Thames, as it was significantly cheaper. The Prime Minister Stanley Baldwin urged the SR to accept the proposal, as "a matter of national importance", but the bill failed in 1930 after the select committee did not accept building a new Charing Cross on the south bank. The proposal was formally rejected in 1936 by the London & Home Counties Traffic Advisory Committee, which revived the double-deck bridge option. The plans were all abandoned following the outbreak of World War II.'
There also seems to have been a vendetta against Hungerford Bridge; I've read a few books about the Thames in which the authors complain about its supposed ugliness.