Pension contributions not made

[DreadingWork]

I'm in a bit of a pickle. Work's Mat Policy states that if I (employee) made contributions based on % of SMP, then my employer would make contributions to my pension based on % of full pay. So I opted to carry on paying my pension whilst on Mat Leave. Random payments were taken from my SMP throughout mat leave & sometimes employers contributions were made, sometimes not. Opening my payslip each month became quite scary in the end! Almost £400 was deducted one month under the guise of "pension contributions".
When I returned to work & talked to HR, they blamed payroll & vice versa. When we went through it all, employers pension contributions were short to the tune of about £2000. I went back to work in June & I'm still struggling now to get anyone to sort this out.
Can anyone help me with exactly what the legislation is surrounding pension contributions during maternity leave please? I hate keep having to badger my HR department & I'm sure I'm getting labelled as a troublemaker. Not sure where to turn next really.

TIA

The policy is correct. Contributions made by the employer during mat leave on a %age basis must be as a %age of full pay. Your contributions as a %age should be based on your mat pay.

So the policy is right, and it's only a question of error rather than anything else. When you say 'we' went through it, do you mean you and HR? In which case if you both found that employers pension contributions were short, what's the problem about getting it paid? The policy (and law) state that x is owed, HR agree that x has not been paid, so what's the hurdle?

Many thanks flowery for the clarification - the hurdle is what I'm not sure about.
I suspect payroll think that in order for me to "qualify" for the employers contributions, then I should have been making contributions based on my full salary, not mat pay. I was beginning to think I'd got the wrong end of the stick, but this makes it clearer.
Back to HR again then....