Shareholders opposed to Blackstone’s buyout of Texas energy concern Dynegy are stepping up their efforts to block the deal.

Seneca Capital, which owns 9 percent of the stock, said yesterday it plans to nominate two executives to Dynegy’s board.

Seneca told The Post that the two board nominees — Hunter Harrison, the former head of Canadian National Railway, and Jeff Hunter, co-founder of US Power Generating — would also purchase 800,000 shares of Dynegy.

The move came only hours after advisory firm Proxy Governance came out against the $4.7 billion Blackstone buyout, which needs a majority of shareholders to approve the deal by Nov. 17.