Green Property has made a firm offer to buy British property group Trafford Park Estates for up to £168 million in its own shares or £150 million in cash.

If the bid is successful, it will be Green's biggest acquisition by far and would increase the size of the Irish property group by around 25 per cent.

Trafford Park, which has postponed an extraordinary general meeting to approve a merger with another British property group, Barlows, has issued the customary statement that it is examining the Green offer and urged shareholders to take no action. The Green offer is, however, conditional on Trafford Park abandoning the proposed merger with Barlows.

The Green offer is marginally higher than was indicated when the group first indicated its interest in Trafford Park last week.

It is understood that Green has framed its formal bid after doing the rounds of the institutional investors who will decide the outcome. Well over 50 per cent of the Trafford Park shares are held by a small number of institutions - four institutions alone control 35 per cent - and the share offer is pitched at this group. Institutions with shareholdings over 3 per cent include Mercury, Brittanic, Morgan Grenfell, M&G, Sterling, United Assurance, Framlington and Robert Fleming. Many of Trafford Park's private shareholders, including octogenarian chairman Sir Neil Westbrook - who holds around 5 per cent - may find Green's cash offer attractive, although Sir Neil has already indicated that he believes the Green offer undervalues Trafford Park.

If the Trafford Park board does reject the Green offer and proceeds with the Barlows merger, the May 29th extraordinary general meeting will inevitably become contentious. Trafford Park has performed poorly in recent years with pre-tax profits falling from £10.4 million sterling in 1995 to £7.1 million in 1996 to £6.9 million in the year to June 1997

The structure of the share swap offer is 46 Green shares for every 100 Trafford Park shares, valuing the Trafford Park shares at 212p sterling and the company at £146 million sterling or £168 million. The cash offer is 190p sterling, which values Trafford Park at £131 million sterling (£150 million).

The offer compares with a Trafford Park price of 159 1/2p sterling, immediately before Green's approach was made public. The Trafford Park shares closed yesterday up 12p on 191p sterling, 1p ahead of the Green cash offer. Green shares were unchanged in Dublin on 530p.