I'm sure Neil can explain why the policy was so destructive .
Right, here goes...
Let me take you back briefly to the introduction of corporation tax. Company A makes a profit of £100 and that profit is subject to coporation tax, let's say at 20%. So company A has £80 net profit. Let's say that company A chooses to pay it all as a dividend. For simplicity, there is just one shareholder so he receives £80 of dividend income. He's a higher rate taxpayer so has to pay tax on it, let's say at 50%. So he is left with £40.
The problem is that, under the system above, the company profit has effectively been taxed twice (at a total of 60%): once at the corporate level and once at the personal level when the profit is distributed. This is called a classical tax system. The theory is that it reduces economic activity as it disincentivises investment in equities.
Back in the 1970s the system was changed to what is called an imputed system. Essentially, when receiving the dividend income, an individual assumes that basic rate tax has already been paid on it. So, basic rate taxpayers didn't have to pay anything further, higher rate taxpayers paid the difference between the basic and higher rate, and those not subject to tax could claim back the basic rate tax that was assumed to be have been paid. This made investment in equity much more attractive.
Pension schemes don't pay tax on investment returns. So under the imputed system, a company put £5m into their company pension trust (along with all the employee contributions) and invested it in equity. They received dividends and, because the pension fund is exempt from tax, got a tax refund on the imputed basic rate tax. As an example, if the pension fund received a dividend of £80 then, with a 20% basic tax rate, they would get a further £20 tax refund, to give total income of £100. This system was part of something known as advanced corporation tax (ACT).
In 1997 Gordon Brown repealed ACT. He did so for two reasons:
1 - Cash. It was worth £5bn a year and was an easy target. He calculated that it would effectively be a way of taxing employers, who would make up the loss in the pension.
2 - It encouraged pension schemes to move away from equity investment to debt (so they earned interest) i.e. he wanted pension schemes to invest in government bonds.
Removing ACT meant that pension schemes no longer got the tax refund so there was suddenly a huge funding problem for all defined benefit schemes. A lot of employers decided they couldn't afford to bridge that gap and closed the schemes to the detriment of the employees.
I don't think it was deliberate, but it ended up being catastrophic for millions of employees and thousands of employers.