Capita shares had fallen more than 14% on Thursday after the outsourcing group issued its second profit warning in three months, and by midday on Friday they had lost a further 3%.
However, overall the market was up, with the FTSE 100 index rising 18.75 points to 6,950.30.
MedicClinic International was the biggest riser on the index, up 4.1%.
The FTSE 100 is on track to record five consecutive days of gains. Financial stocks have helped to bolster the market this week, but there were signs that this rally was coming to and end with Prudential down 2.5% and Barclays dropping 2%.
In the FTSE 250, shares in Euromoney fell 5.7% after Daily Mail and General Trust said it would cut its holding in the company to about 49% from 67%.
On the currency markets, the pound edged up 0.1% against the dollar to $1.2595, and rose 0.5% against the euro to â‚¬1.1913.
The FTSE 100 remained on track for its best week since July, but shares in Capita continued to fall.