The latest cash-for-access scandal engulfing Jack Straw and Malcolm Rifkind has exposed something rotten in British politics. It is abhorrent and unacceptable. We must now overhaul how we regulate the relationship between MPs and external influences.

MPs are elected by their constituents to represent them in parliament. What’s on offer in exchange is an opportunity to deliver real, meaningful change.

We do have many MPs who are committed to that role. Many of us work night and day to get through our work. We find it is the equivalent of having two full-time jobs – one in Westminster and one in the constituency.

Far too many MPs have been here so long a sense of duty morphs into one of entitlement

But there are just far too many who don’t behave that way. They’ve been here so long a sense of duty morphs into one of entitlement. They get caught up with the pomp and ceremony, allowing the link between the public and their parliamentary role to unravel.

At the crux of this failure is our electoral system. Safe seats generate complacency. They give many MPs the opportunity to sit back, knowing they’ll get re-elected again and again. This was captured crudely by a Labour MP recently: even if “a raving alcoholic paedophile” were selected as a candidate, he said, his seat would still be kept.

And it is often in safe seats where some MPs find they have enough time to take on two jobs. Suddenly they believe they don’t need to respond to casework or do the work in parliament. They are above all that – and why shouldn’t they earn £5,000 a day at the end of their careers?

That needs to change. MPs should only be allowed to take up a second job if the circumstances are genuinely exceptional – for example, if they are a doctor and need to do the odd hours so they don’t forget vital skills. But when this is allowed, great care must be taken to scrupulously avoid any conflicts of interest, real or perceived.

In 2010 I was elected to represent the city I grew up in, Cambridge. At the time, I sat on Liberty’s national council. I gave up that role because I knew that it would look questionable to sit in private on the council with Shami Chakrabarti on a Saturday, discussing what she would say to a parliamentary committee, only to then quiz her in public as an MP on a Tuesday. There was no suggestion of corruption, but it would still look bad.

The problem is far starker when we have MPs working for private interests. We just can’t allow members to work part time for a consultancy, part time in parliament. That’s plain wrong. The inevitable result is that organisations will exert unacceptable influence on parliament.

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There is also the issue of “hereditary” MPs, when the status of being a member of parliament is passed down from one family member to another. We’ve seen more and more Labour dynasties: Straw, Neil Kinnock, and Tony Benn were all top players in their party, and all have sons – the red princes – who are either already in parliament or are running for election.

With the rise of professional politicians, whose only experience of work may be as an MP’s researcher or spad – special adviser – the problem gets worse. This creates small, impenetrable cliques more likely to look inwards to the Westminster village, spending their time grappling for power, rather than outwards towards the people they are supposed to represent.

The public are very sceptical of MPs and their honesty, sometimes with good reason and sometimes not. It is down to us to prove we are worth their trust. That means fixing more of the problems of the past, such as those revealed by the expenses scandal. It also means not making new errors. For example, Ipsa – the Independent Parliamentary Standards Authority, which sets MPs’ pay and expenses – has proposed giving MPs an 11% pay rise after the election. This is a bad idea – we haven’t persuaded the public that they should trust us yet, so they are quite rightly extremely sceptical. Ipsa should abandon this ill-thought-out suggestion.

MPs exist to represent their constituencies. Plain and simple. They aren’t there to enable companies to access British ambassadors or to operate “under the radar”.

This moment needs to be seized to transform our system so that it is more open and trustworthy. Some MPs clearly haven’t learned the lesson of the expenses scandal. The public need that to change.