Total Voting Rights

Costain Group PLC("Costain" or the "Company")

Total Voting Rights and Capital

In conformity with the Financial Services Authority's Disclosure and Transparency Rule 5.6.1(R) we would like to notify the market of the following:

The Company's total number of ordinary shares in issue at the date of this notice is 64,647,825 with each share carrying the right to one vote. The Company does not hold any ordinary shares in treasury. The increase in the number of issued shares has arisen from shares allotted to employees who exercised their options under a Save As You Earn Share Option Scheme and shares allotted to shareholders who participate in the scrip dividend scheme.

The figure 64,647,825 may be used by shareholders as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change to their interest in, Costain under the FSA's Disclosure and Transparency Rules.

31 October 2011

Enquiries:

Costain Group PLC Tel: 01628 842444Tracey Wood