Men’s Wearhouse (MW) rejected an unsolicited offer from smaller rival Jos. A. Bank Clothiers (JOSB), saying the $2.3 billion proposal to create a men’s apparel giant undervalues the company.

Jos. A. Bank said early Wednesday morning that it offered $48 a share in cash, a 36% premium over Men’s Wearhouse’s closing price on Tuesday.

The stock hasn’t traded at $48 in about six years and fell back below $40 after a rocky second quarter. Last month, Men’s Wearhouse reported a 28% drop in its earnings and slashed its full-year outlook.

On Wednesday, shares jumped 23.7% to $43.58. Jos. A. Bank was up 5.5% at $43.96.

Jos. A. Bank chairman Robert Wildrick said he made the offer to Men’s Wearhouse CEO Douglas Ewert by phone on Sept. 17, and then sent a follow-up letter.

But Men’s Wearhouse turned down the proposal, which lead director Bill Sechrest called “opportunistic.”

In an interview with The Wall Street Journal, Wildrick later said he would continue pushing for a deal with Men’s Wearhouse, adding he would also accept a counteroffer for Jos. A. Bank with the same premium.

“The Men’s Wearhouse board concluded that the proposal significantly undervalues Men’s Wearhouse and its strong prospects for continued growth and value creation, and is not in the best interests of Men’s Wearhouse or its shareholders,” the company said in a statement.

Men’s Wearhouse also said the deal would likely raise antitrust issues.

In citing its growth prospects, the retailer noted that it expects to open 100 new stores and already has more than double the sales of Jos. A. Bank, its next largest competitor.

According to its website, Men’s Wearhouse currently has 1,137 stores and sells sport coats and suits. It also offers tuxedo rentals.

Jos. A. Bank has more than 600 stores that offer tailored and casual clothing for men.

Men’s Wearhouse, which operates its namesake stores in addition to Moore’s and K&G, made headlines in June when it abruptly fired co-founder and Chairman George Zimmer, the longtime face of the company’s advertisements.

The move came amid disagreements between the company’s leadership and Zimmer, who accused the board and Men’s Wearhouse management of failing to act in shareholders’ interests by refusing to consider strategic alternatives like a take-private deal.

Since Zimmer’s departure, Men’s Wearhouse approved an accelerated buyback program and bought JA Holding, the parent of clothing brand Joseph Abboud, for $97.5 million.

Follow Matthew Rocco on Twitter @MatthewRocco