Valve-control systems maker Rotork said it expected its first-half results to be lower than a year earlier as oil and gas explorers slashed their investments.

Shares in Rotork, which was also hurt by uncertainty arising from political tensions in Eastern Europe and the Middle East, fell as much as 4.3 per cent in thin trade on Friday and were among the top losers on the FTSE-250 Midcap Index.

The company, which makes valve-automation equipment used in the oil and gas, power and nuclear industries, said its full-year margins would be slightly lower than a year earlier.

Rotork maintained its full-year outlook but cautioned that trading in the short-term would remain challenging as the timing of orders was difficult to forecast.

The quarter indicates that Rotork could be feeling the impact of the oil and gas slump sooner than the market had anticipated, Morgan Stanley analysts wrote in a note.

Order intake in the fluid systems unit, which has the highest exposure to the oil and gas industry among the company's units, fell 29.9 per cent in the first quarter. The unit makes fluid power actuators and control systems.

Rotork's overall order intake fell 7.3 per cent.

UBS analysts cut their full-year forecast for earnings before interest, tax and amortisation (EBITA) to £154 million, below an average forecast of £156m by analysts.