Lord Fowler was Margaret Thatcher's health minister in the 1980s when she introduced Section 28, which stopped teachers referring to gay relationships as "normal".
The bill stated that a local authority "shall not intentionally promote homosexuality or publish material with the intention of promoting homosexuality" or "promote the teaching in any maintained school of the acceptability of homosexuality as a pretended family relationship".
It was repealed by the Scottish Parliament in 2000 and the rest of the UK in 2003.
Lord Fowler told London's Evening Standard newspaper: "We have come a long way. [Section 28] was a great mistake and I think it's now recognised as a great mistake and I would apologise for it. It was totally misjudged."
He has since signed a letter calling for sex education to be made mandatory, and suitable, for straight and gay pupils.