Cash for questions is simply bribery - now a criminal offence

Perhaps someone could explain to me why the Bribery Act 2010 is not used against MPs and Lords who accept cash for questions? This weekend's news is full of MPs and Lords who are alleged to have offered to take cash for questions and the Bribery Act is very clear in what constitutes this criminal offence. Section 2 states:

2. Offences relating to being bribed

1. A person (“R”) is guilty of an offence if any of the following cases applies.
2. Case 3 is where R requests, agrees to receive or accepts a financial or other advantage intending that, in consequence, a relevant function or activity should be performed improperly (whether by R or another person).

So as a potential criminal offence of taking financial advantage to ask improper questions in parliament, i.e. questions that would not otherwise be asked, the police should be involved immediately and if they are found guilty then these parliamentarians should face jail.