The recent run-up in staffing firms

TMP Worldwide

( TMPW) and

Robert Half International

(RHI) - Get Report

led an analyst to downgrade the stocks Monday.

UBS Warburg said the upside implied by its price target on the shares no longer justifies strong buy ratings and, as a result, the brokerage cut its recommendations to buy.

UBS Warburg has a 12-month price target of $20 on TMP, which was lately down $1.43, or 8%, at $16.25. It has a price target of $21 for Robert Half, recently losing 62 cents, or 4.3%, at $16.91. The shares touched $12 as recently as Oct. 10.

Since the second week in October, shares of TMP Worldwide have gained 107%. UBS Warburg said it believes the gains are market-related, but also reflect investors' belief that the recent decision to spin off traditional recruiting assets could lead to multiple expansion, or could signal plans to sell Monster.com.

UBS Warburg said it would not be surprised to see TMP sell Monster.com once the spinoff is completed. But it said tax restrictions would likely delay a sale for at least nine months from now.

Meantime, the brokerage said that continued weakness in the labor market could adversely affect the stocks. "We believe the trading outlook may be choppy over the next few months, as a rising employment rate may temper recent enthusiasm for staffing stocks," said analyst Kelly Flynn in a research note.

On Friday, the Labor Department will release the monthly employment report for October. The consensus expectation is that the economy will have shed 10,000 jobs after losing 43,000 jobs in September. Additionally, the unemployment rate is predicted to tick up to 5.8% from 5.6% in the previous month.