Promoting competition among electricity producers is primarily targeted at ensuring low electricity prices for consumers. Producers could, however, withhold part of production facilities (i.e., apply a capacity cutting strategy) and thereby push more expensive production facilities to satisfy demand for electricity. This behavior could eventually lead to a higher price determined through a uniform price auction. In this paper, using the case of the England and Wales wholesale electricity market, we empirically examine whether producers can indeed apply a capacity cutting strategy. We analyze the bidding behavior of producers during high- and low-demand trading periods across trading days and find direct and indirect evidence for producers' successful manipulation of capacity bids targeted at increasing a wholesale electricity price. We also examine whether the regulatory reforms to improve competition were successful at mitigating the extent of strategic capacity manipulation.