Royal Bank of Scotland, Lloyds Banking Group, HSBC, Barclays and Standard Chartered, signed up to an agreement concerning how they pay out bonuses. Others such as Clydesdale Bank indicated they will fall into line.

The banks have committed to applying beefed-up rules on the disclosure, deferral and clawback of bonus payments bashed out at the G20 meeting in Pittsburgh.

This would appear to be good news for anyone (excepting the more antediluvian corners of the investment and banking sectors) who believes a culture of bonus chasing with little regard to the consequences helped create the conditions for the credit crisis.

But there are already worrying signs that current practice will change very little thanks to a combination of woolly wording and the likelihood that when the principles are converted into practical rules, international jostling will drag down standards.

The key principles include that at least 40% of bonuses for senior staff will be deferred over three years. If a bank is more generous, the regulator will be able to penalise it by insisting it holds more capital to absorb losses from this perceived risky behaviour. Similarly, multi-year guaranteed bonuses will not be allowed.

They have agreed bankers will face penalties or clawback of previous payments if their decisions turn out to be flawed.

There are moves towards transparency with banks told to declare the aggregate pay of senior staff.

The regulator will also have a say over the total bonus pot payable by banks if it puts their capital cushion at risk. If this all sounds familiar, it is because these are for the most part slightly tougher versions of pay rules already promised by the Financial Services Authority. The disclosure rules build on banker Sir David Walker’s corporate governance report earlier this summer.

The government showed some steel in getting any agreement at all. After all, it only really has substantial influence over the two banks, RBS and Lloyds, in which it owns a substantial stake. Others such as Barclays have made it plain that they object to restrictions.

Alistair Darling also won a key victory in ensuring the new rules come into effect from January 1 2010 and will cover the current performance year. This reduces the risk of bumper bonuses being announced just months before a General Election.

The problem is there are already cracks appearing in the new regime. Take the prohibition on lengthy guaranteed bonuses which have been a feature of the investment banking sector this year as the strongest players hire new teams.

A source at one bank said: “If they say we can only pay a one-year guaranteed bonus, well then our HR people will tell the guy on a two-year deal that we are going to pay it all in year one.”

There are substantial grey areas. For instance recently appointed RBS executive Brian Hartzer was given 1.99m free shares (worth around £1m) if he stays for two years, no matter what his performance is. The bank said it was to compensate him for awards he forfeited on leaving ANZ Bank. Is this actually a guaranteed bonus?

On top of this, there are signs that different countries are interpreting the G20 principles in different ways. It looks, for example, like the United States will allow banks by using the 40% bonus deferral as a mere example of what should happen, not a minimum standard.

Stresses will come when the Treasury signs up London-based foreign investment banks in particular to the new rules. Subsidiaries of foreign banks are covered by UK rules. If they are structured as a branch, they answer to their home regulator. UK banks are privately adamant that they ensure that when the rules are finalised, they are not put at a disadvantage.Policymakers, who want the new regime to have teeth, are already worried.

One senior politician told The Herald wearily: “At the end of the day the banks will want the rest of the G20 to sign up to all this.”

The politician said he expected banks to fight hard about the interpretation of the rules.

You might think the government would have a bit more leverage with the sector given the billions of pounds of taxpayers’ money used to help prop up the sector.

But, thanks in part to public policy decisions, financial services remains a significant part of the UK economy. As many as three million people work in roles connected to the sector and it has historically provided a quarter of corporation tax receipts.

Signs that institutions are moving to more favourable jurisdictions would not play well in swing seats in southern England and the Lothians, particularly when unemployment is rising.

In short, politicians can have all the agreements they want but unless rules are precise and universally applied, they are worth about as much as a Northern Rock share certificate.