Stockmarket falls have failed to dent investors' confidence in start-up technology firms, venture capital leader 3i said on Thursday.

But the firm, whose portfolio included failed financial news website TheStreet.co.uk, has braced itself for further closures.

3i, which numbers stockmarket star Bookham Technology among its successful investments, credited technology companies for achieving all its �1.04bn returns between April and September.

The figure, which adds the increase in value of firms supported by 3i to the gains reaped from flotations, compares to �295m for the same period last year.

"Quoted markets were receptive to good quality technology [flotations] for most of the period," the firm said in its half year results statement.

"A small number of flotations in the communications, healthcare and software and computer services sectors made a significant contribution to the total return."

Safety net strengthened

But safety margins have been increased by �59m - more than two thirds - to hedge against future closures among 3i-backed firms.

"As a result of difficult trading conditions, we have reduced the valuation of the portfolio by �144m in respect of companies we consider might fail," Thursday's statement said.

A company spokesman told BBC News Online: "You have to consider that figure in the light of the sums we have invested. You have to compare it against a portfolio of �6bn."

The results statement also revealed 3i's international expansion, with investment in firms in Continental Europe, notably Germany and Spain, rising by 79% year on year to �352m.

The company's US offices invested �29m in eight projects during the six months.

Shares in 3i stood 5p higher at 1400p in afternoon trading in London.