Fletcher Building has sliced about 15 per cent from its annual earnings guidance after the prognosis for two major construction projects deteriorated, prompting an overhaul of the firm's bidding processes.

New Zealand shares dropped on Monday, led lower by Fletcher Building’s earnings downgrade, with Metlifecare and Metro Performance Glass also falling.

The S&P/NZX 50 Index fell 101.1 points, or 1.4 per cent, to 7,057.04. Within the index, 36 stocks dropped, eight rose and six were unchanged. Turnover was $207.6 million.

Fletcher led the index lower, down 10.2 per cent to $8.28.

The stock was placed in a trading halt on Friday, but the shares tumbled after the company cut its full-year earnings guidance by about $110 million because of complexity and delays with a major development that showed up during a review of its construction division.

“The market’s had all weekend to speculate, from an earnings perspective it’s come from a more negative side of things – 15 per cent down for the year,” said Michael De Cesare, research analyst at Nikko Asset Management.

“The reaction was quite firm early but when Australia opened it finished up, it had gotten as low as $8. You never know with Australia, given they’re big holders of the name, whether they’ll give the extra hammer blow or in this case they’ve bid it back up.”

The downgrade comes less than four weeks after Fletcher affirmed its earlier guidance with its first-half results, which included just $1 million contribution from its New Zealand construction business, despite gross revenue from construction soaring 54 per cent to $1.15 billion in the first half.

The slump reflected losses incurred on a major construction project, which it didn’t identify, and it kept the identity of the project secret on Monday, citing client confidentiality.

The index’s weakness was partly explained by Fletcher Building’s drop, which is 7.3 per cent of the index, but the local benchmark saw broad-based weakness led from offshore, with the ASX 200 down 0.5 per cent as of 5:30pm New Zealand time.

Auckland International Airport, which gave up rights to a 10 cent dividend, dropped 3 per cent or 21 cents to $6.85. Metlifecare fell 2.4 per cent to $6.05 and Metro Performance Glass dropped 2.1 per cent to $1.43.