(Adds comment from Alpiq, background)
BERLIN, Aug 20 (Reuters) - Knight Vinke wants Alpiq to stop its delisting and the squeezeout of minority shareholders following a takeover by a pension-backed Swiss investment fund, the activist investor said in a letter published on Tuesday.
In May, the Credit Suisse-managed CSA Energy Infrastructure Switzerland fund announced a takeover bid, offering shareholders 70 Swiss francs ($71.52) for each Alpiq share.
While Knight Vinke does not seek to stop CSA's public tender offer, it said: "What we do oppose is being deprived of the opportunity to continue participating as long-term investors in the upside that we see in Alpiq's unique portfolio of hydro assets in Switzerland".
"(...) we and many other investors believe that the PTO massively undervalues the Company and may therefore not tender our shares", Knight Vinke said.
Alpiq said it was mulling its answer to the activist investor's demands.
"The board of directors got the letter and will address this at the appropriate time," a spokesman said in an email. "The response remains to be determined."
Alpiq has been selling assets including Czech coal power plants and engineering services to rein in debt after posting four losses in the last five years, as its hydropower and nuclear assets have struggled amid low European wholesale electricity prices.
$1 = 0.9788 Swiss francs Reporting by Tassilo Hummel and John Miller, Editing by Michael Shields