UK corporate fund deficit seen up 82 pct in June

* Total UK pension deficit biggest since 2006

* Lower equity allocation to beat volatility, regulations

* 50 billion pounds asset loss since September 2007

LONDON, July 1 (Reuters) - The pension deficit of the 200 largest corporate pension schemes in Britain soared 82 percent to 73 billion pounds ($121 billion) in June due to a fall in corporate bond yields, according to an estimate on Wednesday.

Consultancy Aon said the defined benefit pension deficit at the end of June was the worst for three years. Aon estimated the asset loss since September 2007 stands at 50 billion pounds.

Corporate bond yields are used to estimate pension liabilities, which can be extremely volatile.

UK pension schemes have traditionally been more exposed to equity than their European counterparts but in the last few years allocations have been cut to align investments to pension liabilities.

The fall in equity prices over the last year has prompted pension schemes to be five to 10 percent underweight in the asset class compared to their long-term target position.

Pension trustees may also look for further diversification to spread risk.

"This decision not to rebalance is a passive form of asset reallocation and it is indicative of things to come as pension schemes may opt for lower allocations to pure equities," the consultant said.

Proposed changes in regulations may also encourage lower equity allocation, Aon said.

($1=.6029 Pound) (Reporting by Cecilia Valente, Editing by David Cowell)