The worst performing stock on the FTSE 250 is distribution group Stobart, which issued a strongly-worded statement denying a "speculative" story in the Daily Telegraph that alleges that the Financial Services Authority (FSA) is examining a deal that will see Stobart buy a property portfolio from its chief executive. The article says that the FSA decided to review the transaction after being contacted by Cumbria police. "The company believes the content of the article to be entirely false," said Stobart. Trading at precision instruments and controls group Spectris has been strong so far this year, assisted by a healthy order book at the start of the year, the firm has said, sending shares higher. Derivatives broker Tullett Prebon is lower after Nomura adjusted its numbers for the group, highlighting a sluggish April performance in its interim management statement on Thursday. Nomura reduced its revenue growth assumptions for the year by 2.6%, feeding through to a 4% reduction in earnings per share estimates.Potential margin upside at Informa's Professional and Commercial Information (PCI) division has prompted RBS to raise its target price from 530p to 560p for the specialist business publisher and trade events group, helping the share price higher.Bermuda-based insurance underwriter Catlin edges higher after it said rates for certain classes of business are starting to rise after a first quarter that saw an unprecedented number of significant natural disasters. ---BCFTSE 250 - RisersRentokil Initial (RTO) 101.00p +4.02%Renishaw (RSW) 1,741.00p +3.94%Spectris (SXS) 1,539.00p +3.22%Kesa Electricals (KESA) 140.40p +3.01%Hikma Pharmaceuticals (HIK) 844.50p +2.93%Cookson Group (CKSN) 722.50p +2.92%Capital & Counties Properties (CAPC) 174.30p +2.77%Rotork (ROR) 1,791.00p +2.75%Savills (SVS) 422.40p +2.67%JPMorgan Indian Inv Trust (JII) 424.30p +2.49%FTSE 250 - FallersStobart Group Ltd. (STOB) 127.00p -6.41%Tullett Prebon (TLPR) 381.20p -3.00%CPP Group (CPP) 122.30p -2.94%ITE Group (ITE) 248.30p -2.59%Kier Group (KIE) 1,391.00p -1.90%Brown (N.) Group (BWNG) 294.00p -1.77%JD Sports Fashion (JD.) 894.00p -1.76%Betfair Group (BET) 815.00p -1.75%Supergroup (SGP) 1,199.00p -1.64%Anglo Pacific Group (APF) 300.00p -1.64%