Inquiry found female Tory activist's claim 'plausible'.
Ministers say 91% of parents think children need lessons about the risks of sexting
Justine Greening said the alleged behaviour was 'not acceptable' if true.
Ex-police officers have accused Green of having a huge volume of porn on his work computer.
Theresa May's deputy under fresh pressure after allegations
Party leaders and trade unions agree on new system
Prime minister due to meet Jeremy Corbyn to discuss crackdown.